nsgmls is part of James Clark's sp package. The rest of sgml-tools includes programs and files needed by the linux documentation project. It would be nice to be able to install sp in /usr (or to package it as an RPM, which I do), without having this conflict with /usr/bin/nsgmls. It seems that a good way of doing this would be to have nsgmls be in its own package (or subpackage). With virtual package support, sgml-tools could depend upon a package that provides the nsgmls sgml parser so that it could still work if a newer version of sp is installed. Basically, the sgml-tools package is a collection of utilities, some of which come from external sources, that have been combined into one package. This seems to me to be a recipe for trouble.
we will be redoing the packaging of sgml-tools in Red Hat Linux 6.1 somewhat majorly, when the 2.x sgml-tools stuff is a bit more stable. As it is though, it is definitely somewhat of a mess. We will be sticking with the monolithic sgmltools 1.0.x package for Red Hat Linux 6.0, but we will consider breaking the package up into its respective parts for a future release. Point noted.
SGMLtools is dead. DocBook and James Clark's other tools are now included in the powertools distribution, and may or may not be moved into the main distribution at some point in the future.