[riffraff]

doesn't launchd on osx also parse plist xml files? How are those handled?

[feld]

There's another binary that does the processing and the data is sent to the launchd daemon over a Mach-specific IPC channel that FreeBSD doesn't have.

[meepmorp]

OS X has a binary plist format, too. Maybe it uses that to bootstrap and does xml parsing in sub-processes.