Is there a connection between Sam Leffler the BSD contributor at Lucasfilm/Pixar and BSD as the basis for NeXTSTEP/OS X at NeXT/Apple?

As far as I can tell, there is no direct connection. Sam Leffler contributed most to the 4.1BSD and 4.2BSD while at Berkeley [1], while NeXTSTEP was based on Mach which was based on 4.2BSD and developed by Richard Rashid and Avie Tevanian at Carnegie Mellon [2].

Perhaps the indirect connection is that, before Linux, BSD was the natural choice for an open-source UNIX derivative, and Steve Jobs had an instinct for seeking out the leading edges of computing at the time.

[1]: https://en.wikipedia.org/wiki/Samuel_J._Leffler

[2]: https://en.wikipedia.org/wiki/Mach_(kernel)#Development