However, the obvious solution is to use a html browser because of the hypertext capabilities. Writing my own was pointless as there are already numerous useful implementations. The one I've chosen is Chimera, which is written by John Kilburg. Chimera uses the Athena widget set; for this version I have used the Athena 3D widgets, giving it a more modern look.
There is nothing magic about the Chimera program, any html browser will do. It must however be installed under the name of chimera for Siag to be able to find it. Owners of the familiar Netscape browser who don't mind the bugs and bloat may find this command useful:
cd /usr/local/bin ln -sf $(which netscape) chimera