I see that Freespace 2 is on that list. I can hopefully offer a little more information on it as well because I am a big fan of it.
Freespace 1 and 2 are free and can be obtained legally. It had it's source code released to the public a couple of years ago. Fans of the games worked together to create Freespace Open, which can be found in the forums below.
http://www.hard-light.net/forums/
Through this, the contributions made to reviving the game have given the 7-8 year old graphics a complete overhaul, making them look MUCH better.
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A MMorpg called Conquer Online is free to play and isn't on that list if anybody is interetsed. It's not the greatest thing, but it is free.