GPL is GPL. If their thing isn't, they are in violation. They now have deep pockets.
For anything that had no license spelled out, they had and have no license to use it at all.
To be clear: they appear to have no license to distribute your code today, and owe you damages for all the distribution they have done thus far that was not licensed.
To add, if they are still selling it today then it may reset any statue of limitations. I would recommend that you talk to a lawyer, and get them to draft Jetbrains a letter.
There is no statute of limitations for copyright violation, to my knowledge. I gather Germany imposes some pretty draconian time limits for initiating enforcement, but have not heard of others.
As others have pointed out, if they weren't distributing source and passing on the license, this is a blatant copyright violation, and what they were (still are?) doing is illegal.
If you're at all interested in doing anything about it, copyleft.org has a bunch of useful resources.
It turned out that they specified GPL, and so the redistributor is violating the license.
However, if they hadn't specified a license, then the product would be unlicensed. Which would make the redistributor directly violating their copyright.
If source code doesn't come with a license, that doesn't make it fair game. That makes it unusable by any third-parties.
