Hi, At Collabora (my lovely dayjob), we've been working with Valve on SteamOS. Valve are keen to give back to the community, and we've been discussing ways they can help do that, including providing free access to Valve games on Steam to Debian developers last year.
We're happy to say that this has been extended to Mesa developers as well, to say thanks for all the great work. If you have 25 commits or more (an arbitrary number) to Mesa[0] in the past five years, please drop me an email (with 'Steam' in the subject) with your freedesktop username and Steam username. We can then get you access to all past and future Valve-produced games available on Steam[1].
Thanks for all the great work, and enjoy.
Cheers, Daniel
[0]: Or DRI-type stuff in the kernel too. [1]: Currently this looks like https://store.steampowered.com/search/?snr=1_4_4__12&term=#category1=998...