I am developing a library from scratch. If I license it under GNU GPL (or a similar license), which conditions everyone to disclose the source code, does the condition apply to my other projects?
Say I will create an android app that uses the aforementioned GPL library. Do I need to publish it under GPL aswell? Does it need to have the source disclosed even if I am the creator of both o them?
Does the situation change, when other people contribute to the library?
Say I will create an android app that uses the aforementioned GPL library. Do I need to publish it under GPL aswell? Does it need to have the source disclosed even if I am the creator of both o them?
Of course not. There is absolutely no way whatsoever imaginable how this would be even remotely possible. The purpose of a license is to give rights to someone who otherwise wouldn't have them. You don't even need to know copyright law, it's just basic common sense.
Does the situation change, when other people contribute to the library?
Yes. If you use other people's code, you need to acquire a license for that code.
As the author of a creative work, you may choose a license by which to authorize others to redistribute your work. And you are not limited to choosing just one license.
If you choose to distribute a library under a given license, it would be inappropriate to not follow the terms of that license yourself in that distribution. So, if you created an app that uses your GPL library, it would be inappropriate to use anything other than the GPL for that app itself. Not doing so would essentially violate a demand you are placing on yourself. And it violates the spirit of the GPL that you licensed your library under.
However, if you wanted to release your app under a proprietary or different license, you can also dual-license your GPL library, and use the proprietarily licensed version for your app, and the GPL version for everyone else. Trying to single-license the library per the GPL and use it in your proprietary app is a murky land of unknown law. The complication comes from trying to identify the license of the application that has the bundled library.
Say I will create an android app that uses the aforementioned GPL library. Do I need to publish it under GPL aswell?
So, you don't really have to, but you should, and the consequences if you don't are strange and unclear.
