Well then, it would have helped if I knew about the x clipboard earlier
As you two said, I downloaded the source, moved GLee.h to ../HPL1Engine/include/GL/, ran 'make' and it worked beautifully. I successfully compiled Penumbra: Overture. Man, you two are life savers! Oh, and thanks for the tip about rxvt, I'm glad I know that now. It will help SO much when I want to report a problem or something along those lines
EDIT:
Heh, this is kind of embarrassing... It compiled fine, now just how do I play it? ._.'
I tried running overture.bin, but it the screen just flashes black one time and nothing else. Hm.