This is so factually misleading, I don't know where to begin. On the subject of: Now let's say one day you change course and want to close the source for futu

This is so factually misleading, I don't know where to begin. On the subject of: Now let's say one day you change course and want to close the source for future development. That is completely okay. It may not be okay though. If your code incorporates other people's GPL code, you are unable to close that. And due to the "viral" nature of the GPL, the fact that your code may work together with someone else's GPL code could mean that you can't close your own code either. So you have to be very careful. It is true that the GPL does not explicitly prohibit commercial use, but this is not the same thing as being broadly compatible with commercial use. In general, the GPL is hostile to commercial use by a whole variety of restrictions, including the requirement to share source code. This may not be immediately obvious to OSS newcomers who just want to share their code and have people use it freely.