let's not freak out - you can't "steal" open-source code, they used an incompatible license. that was accidentally too free.
people monetizing something you open-source isn't stealing.
If someone else has a better idea of what “forking GPL 3 source code and using a different licence” would be, then please let me and others know.
> "Moreover, your license from a particular copyright holder is reinstated permanently if the copyright holder notifies you of the violation by some reasonable means, this is the first time you have received notice of violation of this License (for any work) from that copyright holder, and you cure the violation prior to 30 days after your receipt of the notice."