A/UX was forked from UNIX System V Release 2.2, with "additional features from System V Releases 3 and 4 and BSD versions 4.2 and 4.3". It also had a TCP/IP stack, since before MacTCP (if I recall correctly).
I don't have any direct knowledge of Apple's licensing issues with AT&T, but I worked for SCO in the early 90s, back when it was a UNIX OEM, not a litigation zombie.
AT&T licensing fees for UNIX back in the late 80s/early 90s were fiendish; that's the whole reason for the ascendancy of Linux today. (Linus couldn't afford his own Intel UNIX shrinkwrap, so he began rolling his own kernel.) I heard a ballpark figure that SCO paid out $200 in royalties every time they sold a copy of Open Desktop 3.0, which included royalties on SVR3.2, a third-party TCP/IP stack, X11 (which was free), and OSF Motif (which wasn't) and IXI's X Desktop (the desktop and utility apps build with Motif/X11). This drove the price of a copy of ODT 3 up to the $1000-2000 mark depending on trim. SCO also paid royalties to Microsoft every time we sold the developer tools, because SCO had inherited the MS C compiler by way of their Xenix license in the late 80s, and SCO SVR3.2 was built using MS C.
The AU/X "additional" features from SVR 3 and SVR 4 was probably the result of a similar process to SCO's cloning of SVR4 features in the early 90s. SCO's UNIX license only covered SVR3.2. AT&T jacked their license prices for SVR 4 so much that going to true SRV 4 would have drastically raised the price of Open Desktop. It worked out cheaper to assign a couple of hundred developers to work for 3-4 years at cloning SVR 4.3 (needed to hit the standards compliance checkboxes required by customers), while keeping the AT&T SVR3.2 copyright declarations in the header files (and on the box).
My guess would be that Apple hit the same wall that SCO hit after 1995; AT&T licenses were too expensive and cloning features and bolting them on top of an ancient code base was also becoming expensive. (As I remember it, SCO bought a license for SVR 4.3 in the end and switched to that, some time in the mid-to-late 90s, too late to dodge the bullet of Linux gobbling up the Intel/Posix world.)
Unix licensing costs almost definitely.
A/UX was forked from UNIX System V Release 2.2, with "additional features from System V Releases 3 and 4 and BSD versions 4.2 and 4.3". It also had a TCP/IP stack, since before MacTCP (if I recall correctly).
I don't have any direct knowledge of Apple's licensing issues with AT&T, but I worked for SCO in the early 90s, back when it was a UNIX OEM, not a litigation zombie.
AT&T licensing fees for UNIX back in the late 80s/early 90s were fiendish; that's the whole reason for the ascendancy of Linux today. (Linus couldn't afford his own Intel UNIX shrinkwrap, so he began rolling his own kernel.) I heard a ballpark figure that SCO paid out $200 in royalties every time they sold a copy of Open Desktop 3.0, which included royalties on SVR3.2, a third-party TCP/IP stack, X11 (which was free), and OSF Motif (which wasn't) and IXI's X Desktop (the desktop and utility apps build with Motif/X11). This drove the price of a copy of ODT 3 up to the $1000-2000 mark depending on trim. SCO also paid royalties to Microsoft every time we sold the developer tools, because SCO had inherited the MS C compiler by way of their Xenix license in the late 80s, and SCO SVR3.2 was built using MS C.
The AU/X "additional" features from SVR 3 and SVR 4 was probably the result of a similar process to SCO's cloning of SVR4 features in the early 90s. SCO's UNIX license only covered SVR3.2. AT&T jacked their license prices for SVR 4 so much that going to true SRV 4 would have drastically raised the price of Open Desktop. It worked out cheaper to assign a couple of hundred developers to work for 3-4 years at cloning SVR 4.3 (needed to hit the standards compliance checkboxes required by customers), while keeping the AT&T SVR3.2 copyright declarations in the header files (and on the box).
My guess would be that Apple hit the same wall that SCO hit after 1995; AT&T licenses were too expensive and cloning features and bolting them on top of an ancient code base was also becoming expensive. (As I remember it, SCO bought a license for SVR 4.3 in the end and switched to that, some time in the mid-to-late 90s, too late to dodge the bullet of Linux gobbling up the Intel/Posix world.)