Two factors when comparing OSX and Linux shares in hw survey.
1) Valve do not like games that are ports and are way more expensive then their originals. Especially if its old game that is ported. The ideal is game sold with SteamPlay (pay once play on each platform you own).
That pushed lots of 3rd party studios who port titles on contract, and sell port independently OUTSIDE of Steam (EU3 have 2 extensions on Steam and 3 more outside of it... etc.).
2) "Others" quite literally mean "others". So you will find there Windows Server, Wine on OSX, Wine on Linux, various Linux distros who do not meat threshold, as well as OSX versions that are too old and too rare.
So its logical mistake to merge Others just with Linux. At least you should split it evenly for OSX and Linux.
Oh and lets not forget that to draw valid conclusions one must have enough data points :P (3 moths hardly are..)
Couple of things. I like the old games and I am willing to play the original half life again for a couple of bucks. Not because I am desperate but for the novelty and nostalgia of it.
Second while it has been mentioned that Linux at 2% isn't enough to sustain the market I think somethings are being missed. If you look at the humble bundle stats, Linux makes up a good share of the revenue. Overall I find that Linux users are a much more engaged user base. Sure windows might have 95% market share but there is a large percent of those users who are just "there". What I wonder is the revenue for the games by OS is. How many of those millions of windows users on Steam are kiddies who just have one game or just have it installed to play the free games and don't buy anything. I think the spending potential for a Linux user is a lot greater than a windows user.
As mentioned there are no triple A games yet, heck I am excited to see the L4D series come to Linux and see the numbers grow even more. Getting games like that out will really start to pull Linux users out of the woodwork. It is all about momentum.