I've ported Mozilla to NetBSD/sparc.  For the less patient (and trust
me, it takes a lot of patience to build Mozilla), there is now a
binary pkg at:

ftp://ftp.netbsd.org/pub/NetBSD/packages/1.5/sparc/www/mozilla-0.m18.tgz

Thanks to dmcmahill for providing access to the victim^Wmachine to do
it on.