The installaton used to be quite simple:

First unpack the tar archive.

gtar xzvf gex-0.3.0.tar.gz

Change into the source directory.

cd gex-0.3.0/

Configure the source package. Optionally add some arguments to configure, e.g. to change the prefix (--prefix=<prefix>)

./configure --prefix=/usr/local

Run gmake and wait of the successfull finish of the compilation process.

gmake

Finish the installation.

gmake install