Can you comment on the extent to which it will be maintained? I understand that you can’t predict the future, but the ever-looming threat of abandonware is always prominent on my mind when I see a tool that looks too good to be true.
I can't predict ultra far into the future (who can these days... :|), but Mutagen has been under active development for about 6 years now[0]. At the moment I have enough funding to work on it full-time until at least the middle of next year, though I also do Mutagen-related contracting and consulting work to support the project. Mutagen's Docker Desktop extension is going to be a freemium product designed to support the project more directly, which will hopefully allow development to continue indefinitely.
Nice work. Depending on your secure networking goals, you could evaluate using the OpenZiti Golang SDK to embed zero trust networking in Mutagen as an alternative to VPNs.