Actually, recent reports have placed the linux user base as finally surpasing the Mac userbase. That would mean that the MacOS port should be dropped if Purebasic was only going to support the top two.
As a disclaimer, I run both the windows and linux versions, but don't own a Mac.
That being said, I'm excited to be seeing a Mac version coming along. As a game developer, I like the idea of being able to move across the three platforms. I'm assuming that 80% of the code is mobile, with only a few things that I would have to develop myself in the short term. To me, that's more than reasonable.
I don't care that the three versions will have different feature sets. As Fred said, the compiler internals are sync'd, hence the same version number. The 'libraries' are another matter (but are close) but that is not hard to work around anyhow. I'll just build my own replacement functions until the real ones show up.
I gotta say, I'm a little tired of hearing Shannara beat this dead horse over and over and over. Fred and co. have heard your complaints on the subject, now move on. If you have some specific graphic functions which you need to have compatibility across OSs Shannara, why not list those and give these guys a priority of functions that would be nice to match? Form the sounds of it, you aren't actually developing on Linux anyhow and are just harping on this thing for no real reason other than philosophical.