Why did DM sue VU?
They were of the opinion that they were the owner of the Enigma code, and no other manufacturer was allowed to use it. VU+ challenged them in court, and they lost (as the Enigma code was GPL licensed).
After which they decided to close the source (and from that create "DreamOS" ), which is also against the GPL license, which clearly states
If you do distribute YOUR APPLICATION, and you used something GPL as part of your application (even if only linking at run-time to a library) - and even if you do not charge money - and even if you do not change that GPL s/w in any way - then you MUST make the source of YOUR APPLICATION available.
This angered many developers who contributed to the GPL version of Enigma and now saw their contribution "stolen". Several of them being PLi developers.
And they weren't already very happy as DMM forced (by payment) many (mainly German) plugin developers to release their code with a license restriction that the plugin may only be used on DMM hardware.
Which is also why the Enigma open source world turned against DMM.
thanks