My primary build computers are Macintoshes, so the Makefile is somewhat Mac-centric. You will have to figure out how to change the Makefile yourself for Linux builds.
Building on OS X You need the Apple Developer Tools installed.
After checking out the code, just create an empty file, "Make.dep" in the top directory and then run 'make.' It should just work.
Building on Ubuntu You will need 'g++' and 'tcl-dev' packages installed.
$> sudo apt-get install tcl8.6-dev
$> sudo apt-get install g++
Create an empty file, Make.dep.
If you installed another version of Tcl (say, 8.3) change the line in Make.ubuntu to read: TCL_VERSION=8.3
Building on Windows You are on your own here, sorry.