Gylfe: No, im pretty sure mektek lost the rights, which is why the free release is no longer available and mektek asked for people to stop sharing it. Im not sure what the issue was, but they also had to stop creating their game AT1BT and moved to Heavy Gear
IIRC, the MekTek release of MW4 Mercenaries was only a partial release that contained just the multiplayer mode. (Feel free to correct me if I'm wrong - going from memory here.)
Gylfe: MS made MW 3 through MW4 and its Mercs and expansions. I think MS still owns the rights, but licenses others such as Pirhanna and HBS to make additional games. I dont think MS owns the general BT IP, just for making video games. They kept the Mechwarrior title for brand recognition after MW2, but its all BT, which began as a tabletop
Actually, Mechwarrior 3 and Mechcommander 1 were made by Micro
prose. Microprose has been passed around by a number of parent companies over the years, but the Microprose brand and some unknown collection of IP appears to have been purchased from Atari Interactive in 2019 by a former Bohemia Interactive developer with the intention of reviving the brand. However, I cannot find anything specific about whether Mechwarrior 3 or Mechcommander 1 were part of this purchase. (They have MW3 and MC1 in a box art collage on their website, but they do not list either of them in their list of developed games.)
...I seriously hate licensing nonsense like this...