I’d just like to interject for a moment. What you’re refering to as iPad OS, is in fact, GNU/Unix/NextSTEP/Mac OS X/iPad OS, or as I’ve recently taken to calling it, GNU plus Unix plus NextSTEP plus Mac OS X plus iPad OS. iPad OS is not an operating system unto itself, but rather another closed source component of a fully functioning Apple system made useful by the NextSTEP corelibs, shell utilities and vital system components comprising a full OS more or less abiding to POSIX.
I’d just like to interject for a moment. What you’re refering to as iPad OS, is in fact, GNU/Unix/NextSTEP/Mac OS X/iPad OS, or as I’ve recently taken to calling it, GNU plus Unix plus NextSTEP plus Mac OS X plus iPad OS. iPad OS is not an operating system unto itself, but rather another closed source component of a fully functioning Apple system made useful by the NextSTEP corelibs, shell utilities and vital system components comprising a full OS more or less abiding to POSIX.
Um ackchyually, Darwin is derived from 4.4BSD-Lite2 and FreeBSD.