The BSD use in there wasn't because of love of standards but permissive licensing. Apple didn't develop CUPS. Apple's relationship with 'standards' has always been pretty complicated although it's mostly worked out for them.
They used BSD because then it could run Unix/POSIX applications instead of the ~0 third party applications that would have existed for a new operating system.
Apple hired the maintainer of CUPS and provided the resources necessary to make it good enough for the publishing market, while continuing to publish the source code. They had enough involvement in RFCs 5227, 5387, 6761, 6762 and 6886, among others, for their company name to be listed in the RFC.
The Unix 'applications' they got for free. The OS itself shipped with a bunch of apps plus the various bits and pieces that now form the Voltron of Xcode and those were all Nextstep apps. Did the Unix part help to market the thing as a workstation? Sure. But, again, this wasn't for love of standards. The actual machine didn't ship with X11. Next didn't, I dunno, join Motif or whatever. The thing was one of the more non-standard workstations around.
X11 didn't even exist when NeXT was founded and its contemporary predecessor wasn't available under the MIT license.
It was often used in the early days of OS X before it had native applications because the X11 version was often better than using Classic, especially after the Intel transition basically killed Classic but not X11.
