Gibson threatening legal action? Oh, what a surprise!
It's hard to know what's going on without seeing the agreement, but my guess is that Gibson is using the sale of Heritage by the original owners to Bandlab last year as an excuse to bully them out of the agreement. Under Bandlab, they have really expanded production and their dealer network which now includes Sweetwater.
BTW, last month Gibson sent a cease and desist letter to Kiesel (formerly Carvin) over Kiesel's Ultra V and California single cutaway, both of which are clearly different from a Flying V or Les Paul. The Ultra V was in production years before Gibson got their Flying V trademark anyway. Jeff Kiesel says he'll fight if Gibson sues.
I also read somewhere that Gibson's program to license a few small builders to copy Gibson designs has collapsed.