To be more precise, my questions is: You have an OpenGL based game running smoothly on OSX, you decide not to port it to Linux. Why?
1. ROI
2. "Have to" offer support for Linux to maintain brand image - very hard
3. hurts game image "game for geeks"
Obviously, it is hugely dependent on the piece of software you have.
Essentially, a sort of background process monitor/snooper that tries to detect cheating behaviour and block or report it. I have no idea if that could be ported to Linux, and whether in doing so they'd:
1) Get grief for requiring it to run as root
2) Fail to detect all sorts of 'easy' cheats, ruining the online services and leaderboards for everyone
3) Interact horribly with the general fludity/flexibility of a Linux system.
4) All or none of the above.
AFAIK it doesn't require root/administrator on Windows and Mac either.
good example of this is with HoN (Heroes of Newerth) where I believe the guy that looked after the Linux port left, leaving S2 having to outsource all their updates every week. The community is fairly good at hacking their way round day to day issues, but it's far hassle free and I'm sure is costing S2 more money than it's making them.