The Rust server isn't dead at all, the maintainer is active but not proceeding until async / await is fully stabilized.
For anyone interested, a detailed list of what is blocking or slowing progress can be found here: https://github.com/ruma/ruma/issues/189
Up until very recently we'd been postponing work due to immaturity of both Rust and the Matrix spec. Now that all the Matrix specs have had stable releases, the main blocker is the maturity of async/await and support for it in the library ecosystem. Since Ruma uses nightly Rust currently, we don't need async/await to be stabilized to proceed, but it does need to be far enough along that it has been adopted by all the major components of the Rust HTTP ecosystem. I'm guessing we've got about six months left until this happens.
Putting my "tech lead evaluating tools" hat on, I like the idea of a single-file binary that can be easily deployed. That said, seeing that the last commit was 2 years ago isn't encouraging :( Given that I'll likely be seriously evaluating potential approaches for our system design within the next 2-3 months, it doesn't look like Ruma would be a viable option for our situation.