Yes, the BSD licence is "permissive" and allows commercial ventures to use the code with minimal obligation or reciprocation on their part. However, the fact that Linux has had a lot more attention with respect to drivers, and the fact that Castle found it more appropriate to work from the GPL'd Linux sources, would seem to suggest that developers don't necessarily care about (or aren't particularly motivated to cater for) companies that take but don't give in return.
So, yes, OpenBSD/NetBSD/FreeBSD might have been interesting from a licence perspective, but then how interesting were they from a technical perspective? Can the level of support from *BSD drivers compare to Linux implementations?
However, I still wonder to this day how Castle got away with the licensing issues (and dubious "BIOS" arguments) around the PCI layer, but I certainly have no sympathy for proprietary software companies and their concerns about competing with open source technologies whilst continuing to deliver closed source products.