As I recall, the Developer's Prerelease requires a PCI bus PowerMac, not a NuBus one. I think it should work on the Beige G3.
This was the first attempt by Be's people to get away from their proprietary hardware (the Be Box) when they realized that wouldn't fly. Altho your disk is labeled "Developer's Prerelease", and I have a similar disk labelled "MacWorld Edition", I don't think they ever released the final version. There was a version for the PC much later; it didn't sell well. Eventually, Palm bought Be and stopped selling anything.
Be OS has some interesting concepts. It was a ground-up design all written in C++ with fairly tightly integrated classes. For this reason, it gets very snappy performance. However, a program written for Be will work there and nowhere else.