These terms explain the rules for using duoBooks. Please read them together with our Privacy Policy, which explains how we handle your personal data.
The short version
duoBooks is for learning languages by reading. You must be at least 13 to use it.
Full Access subscriptions renew automatically until you cancel them in the App Store or Google Play.
Translations and other AI content can be wrong. Use them as a learning aid.
You keep the rights to the books and notes you add, and you must have the right to use the books you import.
1. About these terms
These Terms of Use ("terms") are an agreement between you and Petro Darchyn, who publishes duoBooks under the name PlainProg on the App Store and under the name Petro Darchyn on Google Play ("we", "us", "our"). They apply to the duoBooks apps for iPhone, iPad and Android and to the duo-books.com website (together, "duoBooks").
By downloading or using duoBooks, you accept these terms. If you don't accept them, don't use duoBooks.
2. Who can use duoBooks
You must be at least 13 years old to use duoBooks. In the EU and the UK, if you are under 16, you may use duoBooks only with a parent's or guardian's permission. If you are under the age of majority where you live, your parent or guardian must accept these terms for you. You may not use duoBooks where the law doesn't allow it.
3. Your account
You can read and translate within the free limits without an account. Some features, such as your dictionary, flashcards, collections and Insights, need you to sign in: with Apple or Google on iPhone and iPad, or with Google on Android.
An account is for one person. Don't share it.
Keep your device and your Apple or Google account secure. You are responsible for what happens in your duoBooks account.
We may suspend or close an account that breaks these terms, misuses duoBooks, or puts other users or the service at risk. Where it is reasonable, we will tell you first.
You can delete your account at any time, as our Privacy Policy describes.
4. What duoBooks offers
duoBooks helps you learn languages by reading. It includes a catalog of books, instant translation of words and sentences, explanations, text-to-speech, a personal dictionary, flashcards, and import of your own EPUB and FB2 books.
Translation, audio, your dictionary and syncing need an internet connection. Your mobile operator may charge you for data.
We keep improving duoBooks, so features may change, and we may add or remove some.
We try to keep duoBooks running at all times, but we can't guarantee that it will always be available or free of errors.
5. Free use and limits
duoBooks is free to download and to read books in. The free version has limits, for example on the number of translations, flashcard words and searches. We may change these limits.
6. Full Access subscriptions
Full Access removes the free limits, for example on translations. It is available as monthly, 6-month and yearly subscriptions. The app shows the current price and billing period before you buy.
Payment. Apple (App Store) or Google (Google Play) charges your account when you confirm the purchase, or when your free trial ends. Their terms also apply to your purchase.
Automatic renewal. Your subscription renews automatically for the same period unless you turn off auto-renewal at least 24 hours before the current period ends. Your account is charged for the renewal within 24 hours before the current period ends.
Cancelling. Manage or cancel your subscription in your App Store settings (on iPhone: Settings → your name → Subscriptions) or in Google Play (Play Store app → your profile icon → Payments & subscriptions → Subscriptions). After you cancel, you keep Full Access until the end of the period you have paid for. Deleting the app or your duoBooks account doesn't cancel your subscription.
Free trial. Some plans include a free trial, for example for 3 days, if Apple or Google says you are eligible. If you don't cancel at least 24 hours before the trial ends, the paid subscription starts and you are charged. Any unused part of a free trial ends when you buy a subscription.
Price changes. If the price changes, Apple or Google will tell you in advance under their rules, and you can cancel.
Refunds. Apple and Google handle all payments and refunds, including any legal right you have to withdraw from a purchase. We can't give refunds ourselves. To ask for one, contact Apple (reportaproblem.apple.com) or Google Play.
Your devices. A subscription is for your personal use. When you are signed in with the same duoBooks account, it works on your iPhone, iPad and Android devices. It can be used on a limited number of devices at the same time.
Restoring. If you reinstall duoBooks or change phones, use Restore or sign in to get your subscription back.
7. Books and other content
The catalog. The books in our catalog are works that we believe are in the public domain, or that we otherwise have the right to offer. Copyright rules differ between countries, so a book that is free to read in one country may still be protected in another. You are responsible for following the law where you live.
Our content. The covers, descriptions, reading levels and categories, the short stories written for duoBooks, and the app's design and text belong to us or our licensors. You may use them only to read and learn in duoBooks.
AI-made content. Translations, explanations, examples and sentence breakdowns, and some covers, descriptions, reading levels and stories, are created with the help of AI. They may contain mistakes.
Problems. If you think something in duoBooks infringes your rights or breaks the law, email us at [email protected]. We will look into it and remove it where appropriate.
8. Your content
Your content means the books you import, the words, quotes, notes, tags and collections you create, and any feedback you send us.
You keep all your rights to your content.
You allow us to store, copy, process and display your content, only to run duoBooks for you and to improve it. This includes sending text to our AI, translation and text-to-speech providers when you use those features. This permission ends when you delete your content or your account, except for copies that the law requires us to keep.
Only import books and files that you have the right to use, for example books without copy protection that you have bought, or books in the public domain. Don't import anything illegal or harmful.
We may remove content that breaks these terms or the law.
If you send us ideas or feedback, we may use them freely, without any obligation to you.
9. Translations and AI are a learning aid
duoBooks is a tool for learning languages. Translations, explanations, audio and other AI-made content can be inaccurate, incomplete or out of context. Don't rely on them for legal, medical, financial, safety or other important decisions.
10. Acceptable use
When you use duoBooks, don't:
break the law or anyone else's rights;
get around the free limits, payments or the device limit, or share your account or subscription with others;
copy, modify, decompile or reverse engineer the app, except where the law allows it;
access our servers or content with bots, scrapers or anything other than the duoBooks apps and website;
copy, sell or redistribute our catalog, our content or the AI output on a large scale, or use them to build a competing product or dataset;
overload, disrupt or try to break into duoBooks or our systems, or upload malware;
pretend to be someone else.
11. Our rights
duoBooks, including the apps, the website, the name and logo, the design and our content, belongs to us or our licensors. We give you a personal, non-exclusive, non-transferable licence to use the duoBooks app on devices that you own or control, for your own non-commercial learning, under these terms and the rules of the store you got it from. Some parts of duoBooks, such as fonts, are open source and come with their own licences.
12. Other services
duoBooks works with services from other companies, such as Apple and Google for sign-in and payments. Their own terms apply to those services, and we are not responsible for them. Links in books and on our website may take you to other websites that we don't control. You must also follow any third-party terms that apply when you use duoBooks, such as your mobile operator's.
13. If you got duoBooks from the App Store
If you downloaded duoBooks from Apple's App Store, these rules also apply:
These terms are between you and us, not Apple. We, not Apple, are responsible for duoBooks and its content.
Apple has no obligation to provide any maintenance or support for duoBooks.
If duoBooks fails to meet any warranty that applies, you may tell Apple, and Apple will refund the purchase price of the app, if any. To the extent the law allows, Apple has no other warranty obligation for duoBooks.
We, not Apple, handle any claims about duoBooks, including product liability claims, claims that it doesn't meet a legal or regulatory requirement, consumer protection claims, and claims that it infringes someone's intellectual property.
You confirm that you are not located in a country that is subject to a U.S. Government embargo or that the U.S. Government has designated as a "terrorist supporting" country, and that you are not on any U.S. Government list of prohibited or restricted parties.
Apple and its subsidiaries are third-party beneficiaries of these terms and may enforce them against you.
14. Changes to duoBooks and these terms
We may update these terms, for example when we add features or when the law changes. We will change the date at the top. If a change is significant, we will give notice on this page, and in the app where possible, before the change takes effect. If you keep using duoBooks after a change takes effect, you accept the new terms. If you don't accept them, stop using duoBooks and cancel your subscription.
15. Ending your use
You can stop using duoBooks at any time and delete your account. We may suspend or end your access if you seriously or repeatedly break these terms, if the law requires it, or if we stop offering duoBooks. If we stop offering duoBooks, we will give you reasonable notice where we can. The sections that by their nature should continue, such as those about content rights, disclaimers, liability and governing law, continue after your use ends.
16. Disclaimers
We work hard to make duoBooks useful and reliable, but we provide it "as is" and "as available". To the extent the law allows, we don't promise that duoBooks will be uninterrupted, error-free or secure, or that its content, including translations, is accurate or complete. Nothing in these terms limits the rights you have as a consumer under the law of your country.
17. Limitation of liability
To the extent the law allows:
we are not liable for indirect or consequential losses, such as loss of profits, data or opportunities;
our total liability to you for all claims about duoBooks is limited to the greater of the amount you paid for duoBooks in the 12 months before the claim, or 50 US dollars.
These limits don't apply to liability for death or personal injury caused by our negligence, for fraud, for intentional misconduct or gross negligence, or to anything else that the law doesn't allow us to limit. Keep your own copies of the books you import.
18. Governing law and disputes
If you are a consumer, you keep the protection of the mandatory laws of the country where you live, and you may bring a claim in the courts there where the law allows it. Before you start a legal dispute, please contact us: most problems can be solved by email.