> Capability based security, for example was something that allowed you to run any program, with no danger to your system. It's not part of any common OS. They had it at Xerox PARC, but Steve Jobs chose not to take that part.
For FreeBSD there's Capsicum(1) and for Linux, although the implementation is not strictly capabily-based, there's SE-Linux which depending on the usecase resembles capability-based restrictions.
Also, although not based around capabilities, Linux has supported them for awhile https://linux.die.net/man/7/capabilities