I contacted OliveTree some months ago (late October, maybe?) and asked if they were considering a port to the PRS-500. The answer I got was non-commital, but not negative -- kind of a we'll pass it to our programmers sort of thing. I came away with the impression that they didn't know what the Reader was yet.
I think it might be time to ask them again. If you want to drop them a line, that might be good -- I'd think it'd be best for them to see requests from as many folks as possible.
Edit: Ah, nevermind, I jsut realized I totally missread your post.