Answering some of my own questions:
Is there a good central thread for discussing the move to Discourse that I’ve missed out on? I did a quick search, and it seems to come up in different threads, but I didn’t see a pinned topic or thread that serves as a hub for the conversation.
Jeremy did offer this comment on the aims/intentions of Talk.TW.org I initially missed:
The new Discourse forum at https://talk.tiddlywiki.org/ is an experiment
at this stage. At the moment, there’s two way sync with Google Groups,
but if people like the new system then we will migrate fully over to it.
First, someone is paying for Discourse, right? It’s not free like GG.
Is that the case? I’d thought Discourse was a free, open-source platform — though someone is surely paying to host TiddlyWiki.org, where it’s running. That domain’s been around a long time, and I always suspected it was Jeremy’s, but maybe not. Do we know the identity of our benefactor on that domain? That may go a long way toward reassuring people of the platform’s long-term availability and stability.
Boris is Hero of the Beach on this front, and there’s a whole thread about the costs and his estimates for the future here:
https://talk.tiddlywiki.org/t/paying-for-discourse/