The AT&T lawsuit and the end of DARPA BSD funding and that research group at UCB didn't have a lot to do with that? That was several years after Sun got in bed with AT&T and announced that BSD based SunOS was doomed.
I don't know, but I wonder.
There's also the fact that the internet was far less available in that day and age, making it more difficult to get good people involved.
I don't think it's a big risk, but like I said, I don't think it's impossible either.
Well, look, sure, if you hire all the developers that are working on something and understand it, you can probably out-compete other implementations even if all you have the old developers do on your proprietary project is write up specs from which a different set of developers build a legally non-derivative interoperable implementation.
That may be a risk with permissively-licensed Free software, but its also a risk with copyleft Free software and proprietary software.
Sun Microsystems basically grabbed BSD development by hiring up a lot of good people and running with it. It took a while for the various free BSD's to come into their own.
Basically, with "bsd licensed" software, if a big company hired up all the developers, they could take it proprietary and out-compete fork efforts.
I don't think it happens often, but it's not impossible, either.