Not really a partner in a classical sense as it is a more one way relation.
However we feel that there could just be a broader platform support for GNAT/GPL and a support for a more liberal license than the GPL for the runtime components. And this is what we hope to provide.
You should always be aware that AdaCore has not endorsed what we do and might not actually provide support for the packages we provide.
Most of the GNU tools you can get from http://www.gnu.org/software - however searching the site can cumbersome - so here some more convenience links:
Sadly the Gtk+ project are evenly distributed over the whole internet, some of which are quite difficult to find (especially when a project names itself after a well known city). Here a list of where to get updates to the various source tarballs.