The nx-libs repository contains several sub-modules like nx-X11, nxcomp, nxcompsahd, nxdialog and nxproxy.
Upstream repository of nx-libs (Arctica Project).
$ mkdir ~/x2go && cd ~/x2go $ git clone git://code.x2go.org/nx-libs.git $ cd nx-libs
Depending on what operating system you are, you can create packages for Debian/Ubuntu, Fedora/EPEL, OpenSuse and Windows.
More details about the pre-requisites and the build steps see the README.md file.