I created a system to convert Windows binaries to native Linux/OS X binaries and wrote my own implementation of a ton of Win32 APIs. Never did get Oblivion running, but did run several other games, most notably Prey. Eventually pivoted to implementing DX10 for Linux/Mac/Windows XP (back when Vista was the only one with it), and then the company died a little while later for unrelated reasons. You can read a postmortem here: https://daeken.dev/blog/2009-12-27_Alky_Postmortem.html