I found Universal Binary versions of SDL and SDL_ttf here: http://www.libsdl.org/cvs/. Yippee!
I needed to re-tool the Xcode project files to get it to build, and I finally got frustrated with egobootypedef.h and just re-wrote/re-factored it to make it much smaller/cleaner. Fixed up the rest of the codebase once those changes were in, and voila! It builds!
But of course there’s a caveat. The endian-handling code was mucked up in the process, so certain images are loading with their red and blue channels swapped, and the game crashes once it starts loading models. Probably still works dandy on a Big Endian Mac, but I don’t have time to try that now. So I’ll be working on fixing that up tonight.