MekTek is a web site that started as a forum shortly after the release of MechWarrior 4: Vengeance, but eventually made a collection of mods for MechWarrior 4: Mercenaries, which were released as MekPaks. The MekTek team made three major editions or "MekPaks", the most recent of which was MekPak 3.1. They had planned on making a fourth, but it was never officially released.
Development of the MekTek mods with MP1 (MekPak 1) and was followed by MP2 and MP3. In total, they increased the number of playable units to over 120. They added new BattleMechs, battle armor types, infantry types, as well as new maps and many new weapons. Comprehensive lists of these can be found at the bottom of the page in the "See Also" section. For more information see the section on the MechWarrior 4: Mercenaries page.
Free MechWarrior 4: Mercenaries Distribution
In 2009 it was announced that the MekTek team would be distributing MechWarrior 4: Mercenaries for free via their site, presumably to celebrate BattleTech's 25th anniversary. The rights were finally obtained in April of 2010 and the game was made available for free download.
Ceasing Operations and Switching to Heavy Gear Assault
In 2013 the MekTek web site was suddenly shut down and the free distribution of MechWarrior 4: Mercenaries ceased indefinitely. Currently, neither the full game nor the MekTek mod can legally be downloaded for free from the site. The MekTek team has since started development on a new robot-centered game called Heavy Gear Assault.
Because the MekTek mods were developed completely independent of FASA Studios or Wizkids (MechWarrior and BattleTech's respective IP owners at the time), they should be considered fanon. In other words, they are not canonical, nor are they even apocryphal, which is what the core MechWarrior 4: Mercenaries game was considered. However, several of the designs they added were canonized, such as the Deimos.