It's origins start with AEG and their espionage roleplaying game, Spycraft, which used Dungeons & Dragons 3.0 and even required those books to properly run it. Originally the game was conceived under the title Series Archer, but then the plan was to release with two product lines. There was the generic silver books which expanded every character class. The other line was a campaign setting that featured secret societies and psionic powers. This line was called Shadow Force Archer all in black covers.
AEG updated several rules with a licensed game, Stargate SG1, a Powered by Spycraft product with a core rule book and two supplements before being discontinued.
The next edition of Spycraft saw a complete overhaul of the system. In 2005, Spycraft 2.0 took the OGL as far as possible, it seemed. What came out the other end was an extremely detailed and very comprehensive game system that no other OGL system has yet reached. The book is huge and the rules are so detailed that it seemed most found it completely overwhelming. Many criticizims said that the game was trying to be too much of a general modern RPG toolkit instead of focusing on what was on the tin- spies.
But that's not the end! The guys that created Spycraft and Spycraft 2.0 started Crafty Games, a the new company with the intent to continue the line and ultimately expand it into other genres.
Much of Spycraft 2.0's attention to detail stems from an active Living Campaign and organized play stemming from RPGA which justified such a high level of detail in the rules.
Fantasy Craft is the first and currently the only game released under the Mastercraft system in 2009. It is Crafty Games' fantasy genre toolkit which implemented Mastercraft as a streamlined and slimmed down version of many of the system improvements tried in Spycraft 2.0. The need for such rules for organized play isn't in as much demand these days. Fantasy Craft has seen a rather successful following with an abundance very positive reviews.
Last year Crafty Games officially announced the upcoming Spycraft Third Edition. It looks like the Third Edition of Spycraft will be a bit of a return to what the first edition was like with a more espionage flavored focus with the Fantasy Craft-compatible, Mastercraft system. Crafty plans on leaving other aspects of modern campaign settings to other Mastercraft releases, like for instance, the Ten Thousand Bullets campaign- which will focus on the criminal underworld.
What I like about the Mastercraft system and Spycraft 2.0 is the amount of what the industry calls CRUNCH. This is the d20 version of GURPS and I mean that in the best way. I believe GURPS is the best, most comprehensive system invented for the hobby. Mastercraft/Spycraft 2.0 comes the very closest to that level, closer than any other game OGL I've ever read. I used to believe I preferred system-lite games, but for some reason I find my obsessions lingering on these far more detailed systems instead. Mastercraft is turning out to be one of the best.