The big reason why this library exists is so that downstream consumers can be entirely memory safe in their allocations - it's the same way that the Rust standard library works. Library writers can use unsafe code to provide safe abstractions and APIs, so you end up with an unsafe core with a safe framework on top of it. I'm just continuing that tradition.

I actually haven't read that paper! Thanks for sharing it. What I'm doing is slightly different - it looks like they're building a conservative GC with an unsafe API, much like one might for C. My intent was closer toward building a GC which can be used with any safe Rust code more or less unconditionally.