Question

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Using LGPL library in a commercial Java application

Hello guys!

There is a project under the GNU Lesser GPL license. I want to use this project in my application. Can I sell my application using this license?

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Solution

In a nutshell, the idea of LGPL'd projects (usually libraries) is that you are free to use them as you wish in your own application, be it open or closed source, free or proprietary - as long as you publish the source code of the LGPL'd part (if you modify the LGPL'd part, you must publish the modified sources, under LGPL).

Additionally, the libraries must be linked dynamically so that they could be replaced to another version by the user if he so wishes. For libraries (.dll, .so, .jar...), this is usually self-evident. Side note: this is inherently pointless requirement, because nothing requires that your application works with any other library version than the one that you originally provided. You could even actively prevent your application from working with other versions.

OTHER TIPS

You can use LPGLed libs with your proprietary software, but there are some restrictions you must observe. Better read the LGPL carefully and contact a lawyer.

General notes, You can use a LGPL library if

  • You link with it dynamically only allowing user to replace specific library (for example replace dll to newer compatible version).
  • If you make changes in LGPL code, you release the changed library sources as well.

Generally many closed source projects use LGPL code, it is common practice, but read license carefully, especially this GPL-FAQ.

If you have doubts, contact lawyer.

If you are using the GNU app as part of the development process, then the resulting code is saleable.

If you are calling or otherwise using the public APIs of the GNU app then your app is saleable provided you package and distribute the GNU app as a separate component complete with the original app -- and make it clear in your documentation that you are using the GNU library and it still belongs to its original authors under the GNU license terms.

If on the otherhand you have modified the package, cut and pasted code from the package, inserted your code into thier programs or otherwise changed thier code to get yours to work you can only further distribute with the same gnu license. This does not actually preclude selling the software, but, there are all sorts of complications so its best not to go there.

If in doubt contact the original authors, tell them what you have done/intend and ask them what they think - it is afterall thier software your messing with.

Short answer is yes, you can sell your application under any license you like. The only thing you need to do is:

  1. Mention somewhere that your product uses that library, anywhere, in the about box, in the splash screen, in the manual...

  2. If your customers ever ask for the source code of that library (not necessarily your application), then you must give it to them or tell them how to obtain it. But note that only your customers/users actually have this right (and most customers don't bother right?).

That is basically it in a nutshell though I would still recommend you read the GPL FAQ posted by Artyom.

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