haha, I'm not sure whether the beginning of this thread is sarcastic or hopelessly ignorant.
Unfortunatly DirectX is a proprietary package from Microsoft, and you are not gonna see it Mac, thats for sure! As for the rest it's nice when you have a POSIX compliant system running a strong ruleset of security devices that don't allow most anti-cheats to work, to mention one of the most famous: WARDEN from Blizzard (12 Million players worldwide).
Well... not officially, but it's not the first time the functionality of proprietary software has been rewritten to act exactly the same and then released as open source... ever heard of unix... lol
You've probably heard of WINE (the win-32 library compatibility layer that's been kicking around on linux and BSD for decades), and it's relatively recent porting to OS X, aka crossover in user friendly form... this contains a DX9 compatible substitute library... that effectively is a standalone DX9 graphics library for OS X, BSD, Linux and any other POSIX OS you care to compile it for... since software utilizing DX is only written for windows there's no point in using it outside of WINE.
You should probably make a petition to Valve to make a OS X compatible package of CS and Steam, as you would have more chances of success than having Microsoft porting DirectX.
And indeed they did... while they haven't exactly turned to OpenGL natively, they decided to stick with the result of all their previous efforts to create an engine which uses DX (sensible from the business side of things i guess), this means they also get to keep a single development path for their graphics engine. Instead they wrote a DX to GL layer, this is basically what the WINE DX library does, as all of the OS it runs on use GL. So basically the core engine is the same (but compiled for OS X of course) with the addition of this module that receives all the DX calls and converts them to GL, and it's bloody efficient at it too.
What would be good is if Valve licensed this module so that other windows game devs could release their games on any and all of the platforms supporting OpenGL.