Thanks. I did reinstall Apple's X11, and this time also the SDX files.
I went back to the SwarmX README and cut and pasted into the .tcshrc,
and now I'm finally up and running, going through the simplebug
tutorial, running heatbugs and mousetrap! I'm not sure, but I think it
also turned out to be important that I got the application source code
via cvs from the pserver using the code Bill sent me. I'm still not
sure what I was not doing right with the swrmapps-2.1.1 download.
There is a confusing array of README files, and it's not clear to the
novice which ones are critical--for example, did I need to do a
configure or install, as the SWARM2.1.1 READMEs said? Anyway, I think
I can now move forward.