After the recent compiler changes fixed things for other pkgsrc programs
dramatically I decided to give my long term favorite another try: I rebuild
everything (base + X) and delete all pkgs, then build mozilla-gtk2.

The program now actually runs and displays the gui, but it fails to connect
to any site or display it's internal help/info pages.

So, we are pretty close, but not there yet.

Martin
P.S.: Matthew Green noted that konqueror runs well on sparc64 some time
ago - just in case you need a browser now