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I want to encrypt the SQLite database in my QT application. This tutorial: http://www.qtcentre.org/wiki/index.php?title=Building_QSQLITE_driver_with_AES-256_encryption_support seems promising. But I know QT is licensed under LGPL (and I'm not allowed to purchase a commercial license due to some reason) and LGPL has some restrictions against code modification. Can I: 1) follow the tutorial; 2) use the modified QT with LGPL; 3) keep my application close-sourced?

Karla
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    I'm voting to close this question as off-topic because **it is about licensing or legal issues**, not programming or software development. [See here](http://meta.stackoverflow.com/a/274964/1402846) for details, and the [help/on-topic] for more. – Kevin Brown-Silva Jun 04 '15 at 23:42

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You would have to redistribute your modified QtSql library, and so you would have to distribute the complete, machine compilable source code necessary to build that library.

Your modified library would remain LGPL which means you would have the same rights/responsibilities using it as you would if you used the standard Qt distributed one.

This means that if your application's current usage of the Qt library is permissible under the LGPL, then using the modified library in the same way is also permissible.

I Am Not A Lawyer. This Is Not Legal Advice. I Am A Random Person Who May Not Have Your Best Interests At Heart. I May Be Ignorant Or Malicious Or A Monkey Randomly Hitting A Keyboard.

OliJG
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  • Thank you, OliJG. Seems the tutorial just simply makes a new QT plugin, and the operations doesn't look like "modifying QT source code", so even the productd QSqlCipher dll is LGPL licensed, I can keep my own application close-sourced. – Karla Aug 03 '11 at 02:43
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    You are adding to the existing LGPL Qt SQLite3 driver, creating a derivative work that is also LGPL. Assuming you are linking correctly, your application can remain closed, however you are required to provide the complete source for the LGPL library that you modified and are using. Above disclaimer applies. – OliJG Aug 04 '11 at 02:14