TBH I failed to build bitcoin on windows, I do not have a MAC, and it all works flawlessly. However you should IMHO set bitcoin apart from the BSD and Other, and instead insert some Unix and other option.
For example, I have a pal who is working on porting the bitcoin client to Solaris on an Ultrasparc3 Sunfire. I guess he would be affronted by being pushed into the Linux, BSD and other category
I listed what I believe to be the supported build configurations, which is my intended purpose, not the family of the underlying OS itself. I have nothing against other flavors of Unix-like systems, I am just unsure whether they can use the existing code and makefiles and have everything just work.
There is some flexibility in the interpretation of "or similar" for the Linux or BSD option because I recognize there are varying degrees of similarity between Unix-like systems. I would say if bitcoin compiles and works with little or no tweaks, then it is "similar" for the purposes of the poll.
If your friend cannot easily compile, and is having to port
to Solaris, then I would say that would belong in the 'Other' category, not because it's in any way inferior or not Unix-like, but simply because it's not similar enough to a supported configuration.