with no documentation for that project, good luck. There are 14+ versions of a file which would be a terrible use of subversion.
I loaded "ratSLAM_14.c" and it compiled with a few warnings, but no errors. Since it includes a few other files, you need to load it from the full directory you checked out with subversion.
I have never seen a slam implementation for the NXT. It would be an interesting project to know more about, but I do not see a link to any more information. Where did you hear about it from?
Actually I changed the code a little, to match my bot, and it seems to be doing stuff - wow. Anyhow, that seems to be a pretty advanced SLAM; http://itee.uq.edu.au/~milford/Mapping/Mapping.html
Im hoping to get something a little simpler working, but it looks like real good code to look at to see how they did some things.