I get what you're saying, but on a strictly legal standpoint, everything Hashicorp is doing is by the books...all previous versions of Terraform will remain under the old license and everyone can still use Terraform without fearing a future lawsuit, as long as they stick to those version. So no one made any legal missteps here, neither the users nor Hashicorp.

I think its the ethical side, rather than the legal side, thats more complicated...the contributions from the community contributed to the Terraform "brand" that got bigger and bigger, and now Terraform is attempting to secure their monopoly on capitalization of the brand when previously there was an implicit understanding that the "brand" was open-source.

However, you might also argue that there was an implicit understanding on Hashicorps side that the community wouldn't build directly competitive projects when they held the lions share of the funding on the contribution/maintenance side...

I think the whole thing is pretty complicated - is Hashicorp leeching off of the contributors or are the competitive contributors leeching off of Hashicorp? Honestly I see both sides.

The beautiful thing is that its totally legal and acceptable for OpenTF to do their own thing and continue Terraform under their own terms...so either way we get to see this play out :)