The cynical view is that it is now official Plan 9 cannot be used to make money anymore, so waiving away the remaining monopoly rights one may have over it is free positive publicity

9front continues to be developed, and though all its changes are permissively licensed, the whole is still gpl'd for obvious reasons. This allows 9front's code to be opened up.

Most big ideas have cyclical openings where they can be applied. Kind of like a Mars transfer window.

So, if something had a window 20 years ago, but didn’t get applied, there’s a good chance that another window has opened up.

probably, but if this publicity works, there's a slim chance that the open source community might be able to rally behind it and cobble together a larger interest/community and application base to make it a viable personal product.... all big IFs.

Maybe the patents have run out? or any possibility of being sued for infringement.