i have a friend who works there and i believe it's a proprietary set of stuff...i know that alot of people there are good with perl so i believe it is a perl-based custom language they have developed...
no idea about the database, but i don't believe it's mysql...
there's yahoo...i think that speaks for itself...and you could probably find a ton of articles around the web about it all...try searching news.com and maybe dig around sitepoint.com in their articles...
good luck...v