Earlier quoted context omitted.
In polls here, more respondents report running OS X than report running Linux on their desktops and laptops. So, it is uncertain whether it will ever be the case that the majority of devs use Linux although I guess there's a good chance of it happening if Apple ever decides to abandon the desktop / laptop market.
That or if someone invests heavily enough into building a coherent linux desktop. There are a lot of great things about linux and some of the desktops are quite good (gnome 3.4+, kde) but they just aren't quite there with the small glitches and annoyances that come up just often enough to be off putting for end users. I think linux or another free OS needs a huge backing to make it mainstream and we may see that with…
Don't work on open source, unless you do everything each person wants (and these may be conflicting) then someone will decide it isn't open enough regardless of the actual license.