As I posted there, this directly affects my open source project which is heavily tied to TinyMCE so I may end up forking, and reducing down to what my project needs to reduce maintenance scope & burden.
TinyMCE have been jumping around with their licensing. They were under LGPL, with some (what I believe were) misleading guidance into meeting the LGPL (they specified rules about keeping specific branding elements). They then jumped to MIT, and since moved some of the open plugins to their commercial offering. Now they're making this change.