glibc is the main C function library for Linux and is pretty essential, it's probably best not to muck around with it unless absolutely necessary. glib is a function library for gdk/gtk, so I guess that's why you'd need it to install gtk. Maybe try http://rpm.pbone.net/
or something like that for the version you need.
cvs stands for concurrent version system and is used to update your source tree for a given app without downloading the whole source (ie it just updates what needs to be updated). You can use it to get the latest (developmental) code for something, but you are better off finding a release version for stability.