http://sourceforge.net generally have Open Source GNU software and are a reliable site.
They have this software listed for download and it appears that Astrotortilla and astromate are related by blood since the home site link for astromate is to astrotortilla.
This would mean it is related to the
Astrometry.net project.
That's about all I can see on the program.
Have a look at this too. It might be of interest.
http://www.ideiki.com/astro/ [APT - Astro Photography Tool] the free version is prob enough but the paid version is only 13euro
Trevor