The BeOS community is mainly x86, but there are also a few PPC (Mac and BeBox) users. German YellowTAB is hoping to release a "BeOS" (named Zeta) 6.0. Betas are out, but it hasn't been received well by the community. Remains to be seen if they can release an ok product and stay in business. (so far x86 only)

There is, however, the OpenBeOS project, which -is- targetting the PowerPC in addition to x86, and a port to the Pegasos has been initiated. The ETA is pretty much unknown though. (ie, don't hold your breath)

Adding a BeOS compatibility layer to MorphOS using the libraries of BeOS violates copyright. The "free" version of R5, Personal Edition, was x86 only. Disregarding that, it's still probably one heck of a stunt to pull off.