PABX Support For Open Operating Systems?

LinuxOnEveryDesktop asks: "I am currently investigating which PABX has the best support for open OSes. I would like to see who's calling on the PC screen, run voicemail server software, do PABX administration, call logging, etc., on an Open OS. Most PABXs (like Lucent's Argent Office,...) come with Windows software, which is not an option for my employer."