In VirtualGL 2.3, a custom prefix can be defined using the -DMAKE_INSTALL_PREFIX option of cmake. However, this does not change the paths in the shell scripts (rr/vglrun, rr/vglconnect, etc).
Can this be fixed, together with the ability to use the GNU installation layout? E.g. docs should not go in $prefix/doc, but $datadir/doc ($datadir=$prefix/share).