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.

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.

No. Contempt should be accountable.

If they've done it to you, it's very possible they've done/do it to others. You should post your story. JetBrains is not a little operation and should to be held to account if they've done what you've said.