The only requirement is a C compiler. If you have some kind of Unix or Linux system, you almost certainly have one already. If you have Mac OS X, you may need to install a developer toolkit, which should come for free with Mac OS X. If you have Windows, you can get a C compiler from various places, such as MinGW or Cygwin.
This procedure should be suitable in most cases.
There is a Debian package.
The Makefile in the src subdirectory holds the commands for compiling the glam2 programs. (Likewise for the purge subdirectory.) The commands are customized for the widely-used gcc compiler. To use a different compiler, you may have to modify the Makefile. The Makefile is very simple and commented, so this should be doable even if you know nothing about makefiles. However, you will obviously need to know what commands are suitable for your compiler. Use compiler options that make the resulting programs as fast as possible.
The programs can also be compiled directly, without 'make'. For instance, to compile glam2mask, move into the src subdirectory and type:
cc -Wall -O3 -o glam2mask glam2mask.c alignment.c fasta.c util.c -lm
Modify as appropriate for your compiler. Look in the Makefile for commands to compile the other programs.