This is a useful post that hasn't been updated for a while... may I suggest the following changes regarding the COMPUTER GAMES part?
COMPUTER GAMES
1. Why aren't there CGL-branded BattleTech computer games?
A simple reason: CGL doesn't own the electronic rights to BattleTech. Microsoft does. They licensed these to Smith and Tinker, who's working with Piranha.
They already released MechWarrior Online and are in the process of developing MechWarrior 5 which is single player game, campaign mode FPS.
There's also MechWarrior Tactics at http://mwtactics.com/. I think it's in beta, but I don't know. (this is cancelled)
There is also the BattleTech γαμε being developed by Harebrained Schemes. BattleTech is a Turn-based tactical/campaign game which had a tremendously successful Kickstarter campaign.2. So if there are no computer games, how can I get my BT fix?
The best option (IMHO) is MegaMek. It's faithful to the board game, so if you like the tactical perspective rather than the first person perspective used in the MechWarrior franchise, you're in luck.
MekHQ (from the same team of MegaMek) is the campaign module, and MekLab is the TechManual module of MegaMek. There's more info at the MegaMek site,
http://megamek.info/.
MechCommander, MechCommander Gold, and MechCommander 2 used to be available for free download, but I can't find valid links anywhere. (Though Microsoft has made the MechCommander Source Code available for download so if you're a programmer you can use that as a starting point.)
If you prefer the first person perspective,
but don't want MechWarrior Online or cant wait for MechWarrior 5
you're out of luck. For a while the MekTek team was distributing MechWarrior 4, and there is
was a BattleTech-flavored expansion to Crysis called "MechWarrior: Living Legends".
but those have been taken down.