I've been wanting to make my own open-source project under the GPL. However, I was thinking of making a paid professional version that adds features that are closed-source. Is this possible?Edit: Am I allowed to charge a small fee for the compiled source?
Can you commercialize your own GPL product?
licensing;gpl;open source definition
If you own copyright to all of the code in your project, then yes, you may grant other licenses, to another enhanced version or even to the exact same code.However, if you've made your project GPL, then once you have accepted a patch from anyone, then that contributor also owns a part of your code and would have to concur in the professional license, or else you would need to refrain from pulling the contribution into the other version.These points are well covered in @apsillers' thorough answer to this question.You may charge any fee you like for your professional version, and in fact you may charge any fee for the GPL version, too, according to the Frequently Asked Questions about the GNU Licenses.