This seems like an odd description. TeXmacs may be the only implementation of the format, but it seems well-documented and the code is all free software. I don't think I'd call it a proprietary format.
I like the idea, but the execution wasn't that good. It really didn't felt as something i could rely on at all.
We tend to use git repos + XeLaTeX in my group.
The interface was somewhat clumsy in the early years (around 2005 or so). It wasn't responsive and a lot of things were unintuitive.
Some things simply didn't work. There was a concern that if something broke, it might never be fixed.
Keep in mind that my usage ended about 15 years ago. Maybe it's better now, but LyX was a good alternative, and I've never had a reason to move. It can be hard to overcome a slow start.
edit: the bugs are real though, no denying that.
Your mailing list archive is not indexed by google (except for the narkive version, where search is broken) so answered questions are generally not visible to new users.
The default search in the list archive only searches a single month, this is useless. Searching multiple months is non-obvious.
Some project-deaf suggestions from this outsider are:
- put your lists on Google Groups so they are easily searchable and findable for new users
- just put the damn thing on GitHub and use their Issues system (or GitLab or at least something that isn't Savannah).
It might be a bit annoying for current project members to get the hang of it but I think, in 2020, it is very difficult to grow and show off a community that's based on GNU Savannah!
a Gitter room:
https://gitter.im/texmacs/Lobby
and a GitHub mirror here:
https://github.com/texmacs/texmacs
where you can post PR. As for Bugs we prefer the savannah bug tracker but if you post something on GitHub we will take it in consideration too.