I've uploaded a binary pkg for Mozilla at:

ftp://ftp.netbsd.org/pub/NetBSD/packages/1.5G/powerpc/All/mozilla-0.m18.tgz

All the changes to make the pkg build from source are checked into
-current pkgsrc (plus a GCC/G++ configuration fix, for which you'll
need to rebuild the compiler).

Shar and enjoy.