But I disagree. It's not extorting money to sue someone who stole your code and deliberately removed your copyright notices. The open source license only gives you the right to use the work for commercial purposes AS LONG AS you comply with the terms of the license. If you don't, then you're illegally profiting off stolen work. You can't violate the terms of a contract while still benefiting from it.
I don't know how much was stolen here, but if it's foundational enough to the project that HBC had to give up development, then they might have a case, but IANAL. Not doing anything though would mean letting them get away with their ill-gotten gains (again - if true), and I just don't think that's right. Like I said, I've seen similar things happen before and it pisses me off.