I was able to speak with someone at TinyMCE on a Zoom call this week and we had a good meeting. They are going to make it possible for us to continue using TinyMCE 7.x+ in the core, even though it is using a GPL license, while we use the MPL 2.x license. They will make a custom license available for ProcessWire and I hope to have the details of that potentially next week. We’ll have to review the conditions and everything to make all is good, but it sounds like it will very likely solve the issue for us. I’m really happy about this and look forward to working with TinyMCE 7.x
They also expressed interest in us potentially collaborating on a separate module that would make some of the commercial and advanced TinyMCE features available to ProcessWire users that wanted them via a paid service, like a Pro module. This option hasn't been available to us before, so I thought it sounded interesting. I'll definitely be communicating with them more about that to see what's possible. That’s all I know so far, but will keep you up-to-date as I learn more.