[ moving to fpc-other ]
Thaddy wrote 12 lines
If you did write "use as you like" in the license, they indeed can make derivative versions that are closed source and you have no rights to those derivative works. However, what DoDi mentioned is correct: you still have the rights to the original version of the source code that you wrote. So there is no need to get anything "back", as you still own what you owned initially.
Additionally, they cannot deny that you are the author of the original source code on which their derived version is based, at least in mainland Europe (to be recognised as the author it's part of the "moral rights" section of the author's right, which simply cannot be given away regardless of what you say, write or sign). I don't know in what way this needs to be recognised though, but a note in the source code would seem appropriate. These moral rights do not exist in Anglo- Saxon copyright, but since they sell worldwide they have to take into account copyright law in all jurisdictions they sell their software.
Jonas
