> The service provider says that prospective users MUST give up that right in order to use the service.

FWIW, that's well within the service provider's rights. (See also: RHEL)

But that's not what Bambu has done here; instead of simply locking down their services (like RH does) they sent legal nastygrams to folks that modified the software that they themselves published... while also directly violating the upstream license terms of that same software.