There used to be binary packages for Solaris that someone made, but the packages seem to have disappeared (it was an old version of GNOME anyway). If a good set of binary packages for any of these systems becomes available, we can probably put them on the FTP site.
In absence of a binary version, you're going to need to use the tarballs. If your system doesn't have a compiler, the GNU Project offers the GNU C Compiler (gcc) for Free on pretty much every platform out there. Go to http://www.gnu.org/software/gcc/gcc.html for more information.