The link on this page is to the development release 7.8, but some programs prefer the stable release, 6.5. Check which one your programs need. If the ./configure script for the program says that it cannot find ClanLib you have probably got the wrong version.
Also, the download link for the Hermes dependancy on ClanLib's page is broken. The correct link is:
a kickass game SDK!!!
It's the best.
An open, cross-platform journaling program.
A scientific plotting package.