I wonder if things are different on the BSD side versus the Linux side. Just a guess, but Linux kernel development has always had a sort of anti-academic view, perhaps soured by the early Tanenbaum-Torvalds flamewar, whereas much of BSD was actually written by academics (the name comes from UC Berkeley, after all), and collaboration still seems reasonably common. There might be some downside to Linux being so popular, as well: it's now the default option, so people who just need something, anything to test on will pick Linux, whereas my guess is that people modifying, say, the NetBSD kernel for academic work are more interested specifically in NetBSD and contributing back to it. Solaris development also long had a close relationship with academic researchers working on Solaris, for whatever reason (probably Sun actively making efforts, including hiring academics for summer consultancies).
> Just a guess, but Linux kernel development has always had a sort of anti-academic view,
That doesn't prevent almost all realtime-related academic papers and research to be focused around linux. Simply put linux is practical. It has a large mind-share, it has a lot more drivers, and most importantly it is being very actively developed.
Sadly enough a lot of academic-only projects last on average 4 years before they die off -- that is usually the time someone takes to do their PhD.
One can also argue that realtime OS-es are largely driven by a practical need from the industry side of things rather than from an academic perspective.
> the NetBSD kernel for academic work are more interested specifically in NetBSD and contributing back to it.
That also means one would have to be a NetBSD enthusiast and also a realtime enthusiast. The intersection of those 2 sets is probably fairly small.
