What was unique or interesting about OSF? There's quite limited resources online.
Sun was an exciting company with its own vertical technology stack, and I was always surprised that they never made a serious attempt at making Solaris the developer workstation of choice. To do this they would have needed to (1) maintain a first class web browser environment; (2) provide a less sucky window manager; (3) multi-monitor support; (4) something that handled PDFs nicely; (5) an adequate non-console email client. Something like Java but with a better GUI layer would have been nice too. They bought the Lighthouse guys but then didn't use them.
Solaris had a significant technology advantage over NeXT, an established base in enterprise (a lucrative marketplace and much more forgiving than home desktop).
Ironically, while Sun were busy burning their OpenStep stack, NeXT were embracing Java and that kind of saved NeXT. It allowed independent NeXT developers to ride forward on a maintained technology stack (WO/Java) while Apple retooled.
Would be interested to know anything at all about OSF, and what distinguished it from SVR5.