Mike Cohen (mmcohen at ssyx.ucsc.edu) has had a ditroff priviewer available via anonymous ftp from ssyx.ucsc.edu (128.114.133.1) for several months now. it's in pub/unix-misc/dsee.sun3.tar.Z the binaries there are known to work on sun 3.4 and sunos4.0. mmcohen at ssyx.ucsc.edu will respond to questions, i think.