@Gene: It wasn't F/OSS, no, but I'm not sure where the "closed as hell" comes from, in that is was no more closed than any other desktop operating system. Be definitely caught a lot of hell from the Linux fanboys, basically for not being Linux.
@kain: No, BeOS was designed for its own system, the BeBox, which happened to be based on the same chip as the Mac at the time, which meant that porting it to the Mac would have been much simpler than porting it to x86 was. Gassee tried to sell BeOS to Apple, who wanted to pay far less for it than he wanted, and, of course, Jobs was making his comeback and brought NextStep in instead. Be then made a move to the x86 platform and tried to position BeOS as a competitor to Windows, which failed in part due to Microsoft's efforts to keep OEMs from bundling any competing operating system with their computers.
The lack of apps was definitely an issue, so Be pitched the OS at specialist users such as graphic designers and sound engineers who could make use of the pervasive multithreading and high responsiveness of the UI, but it never really took off in that market. It was definitely unfortunate, because it was the most responsive and advanced OS, from a user perspective, available in the market at the time, but the company didn't really have a notion of how to sell it, especially against Microsoft's market power.