tar xvfz GF-2.8-i386-pc-linux-gnu.tgz cd GF-2.8-i386-pc-linux-gnu ./configure make installYou may need sudo make install; if you cannot write in /usr/local/, you can change the target directory by ./configure --prefix=MYDIR.
Don't forget that you can always get the current sources from the GF Darcs Repository. First time you do
darcs get --partial --set-scripts-executable http://www.cs.chalmers.se/Cs/Research/Language-technology/darcs/GF/and subsequent times
darcs pull -aThen compile and install as described in GF/src/INSTALL.