I wonder how many of the features which other operating systems got much later, such as the unified buffer cache, were due to worries of software patents?
UBC is one of the more technically challenging things to retrofit onto BSD, see https://www.usenix.org/legacy/event/usenix2000/freenix/full_... -- in particular note that it wasn't a universal performance improvement as of that paper. Some long lived UNIX like HP-UX never accomplished it.
