Valve wants to speed up development time of games that get ported to Macs. Since Macs and PC’s are like apples and oranges, developers can’t use the same methods when trying to optimize a game on both platforms. Valve has decided it will lend a hand to developers by releasing a portion of its own graphics code.
Steam was released for Mac earlier this year. However there is still a disproportionate amount of games on Steam that are not Mac compatible. Developers are free to use Valve’s graphics code, but they must agree to implement Steamworks in their titles. To compare this situation to a sports analogy, Valve will loan developers the equipment but developers have to play on Valve’s field. Steamworks allows developers to use all aspects of the Steam service in its games. This isn’t a bad trade off if you consider the amount of exposure a game can get on Steam. At any given time, Steam has over 1 million users logged in simultaneously.
Valve also noted that the number of Mac compatible games sold on Steam has increased between 15 and 20 percent since May 2010.