Capability Operating Systems

This week Ben Laurie asks about capabilities in mainstream operating systems. Coincidentally, I was also tasked to investigate Mach Ports this week. According to the GNU Hurd wiki, "Mach Ports are Capabilities".

Okay, GNU Hurd is not exactly mainstream. But OS X is now installed in almost 11% of the computers in the US (arguably higher in more technical user populations). And Mach Ports are clearly part of OS X (including iPhone), but not widely used. Michael Weber points out that his IPC example code has found its way into the Chromium project. Maybe it's just a coincidence that Chrome was the only undefeated browser at the recent CanWest security conference in Vancouver last week.

So I am left to wonder what is the difference between these two concepts of capabilities, and what does Ben think OS X needs. Is it just a matter of making these services more visible?