HappyKillmore's very cool GCS is now officially supported in the APM manual
. It's still in development, so some things are not working quite right and not fully documented, but it works well enough to use now and will only get better.
This is just the first of several GCSs that will be supported. The orginal LabView GCS is being updated for APM, and the very cool PixHawk GCS (QGroundControl)
that James Goppert is porting is close to being ready for prime time, too.