bison for ppc64 isn't on RHN: https://rhn.redhat.com/network/software/channels/packages.pxt?upper=20&filter_string=bison&lower=1&alphabar_column=NVREA&cid=2894 And it's also not available on the nightly install trees or ISOs for RHEL4 PPC.
Please explain how this is a problem. I don't see why the ppc package is insufficient.
Because in addition to bison, there's a static library called liby in bison. To compile an application that uses this library natively (not in 32-bit mode) we need a 64-bit bison.
At this point, we are not adding more multilib development code to RHEL 4; this should be fixed in RHEL 5.