I created an icon for an Android app with the tool Android Asset Studio. The code of this tool is licensed under Apache 2.0. But I cannot find any copyright info on generated icons.
Are they automatically also licensed by Apache 2.0 (not what I would assume) or am I free to use them however I like (e.g. under the GPL-license)?
To be precise: I did not include any of their code into my project, I only used the tool to generate an icon, which should be part of my project.
The GPL FAQ has an item describing this case (which has applicability to copyright law in general, not just the GPL):
Is there some way that I can GPL the output people get from use of my program? For example, if my program is used to develop hardware designs, can I require that these designs must be free?
In general this is legally impossible; copyright law does not give you any say in the use of the output people make from their data using your program. If the user uses your program to enter or convert her own data, the copyright on the output belongs to her, not you. More generally, when a program translates its input into some other form, the copyright status of the output inherits that of the input it was generated from.
So the only way you have a say in the use of the output is if substantial parts of the output are copied (more or less) from text in your program. [...]
Since the icon is not composed of pre-existing material whose copyright is held by someone else, the copyright of the brand-new icon belongs to you, and you may license it however you choose.
Note also that even if some part of the icon was copyrighted by someone else and given to you under the Apache 2 license, the Apache 2 license is compatible with the GPLv3. In that case, you could license your part (and the compilation as a whole) under the GPLv3.
