As a long time GNU+Linux user, I would be fine with being forced to use Linux or FreeBSD. As a matter of general principal, however, I am opposed to such OS req

As a long time GNU+Linux user, I would be fine with being forced to use Linux or FreeBSD. As a matter of general principal, however, I am opposed to such OS requirements when they extend beyond reasonable security and comparability concerns. I wouldn't work for a company that required employees to use Windows, OSX or Solaris.