Microsoft wanted to kill of upstart Netscape so they changed the Windows NT license and pricing. NT Workstation became limited by the license to a very small number of clients, regardless of what server software you wanted to run on it.
For more than a handful of clients you were required to purchase a much more expensive server edition which was basically the same, but included IIS, Microsoft's web server. In other words, to legally use Netscape's (or anyone else's) web server on Windows NT, you still had to buy Microsoft's web server.
To the contrary: it happened to _my_ company, with a minor detail that I omitted: what they objected to was having the software preinstalled _and visible on the desktop._ The end result was the same.
Our company sued Microsoft over it. There was a settlement.
For more than a handful of clients you were required to purchase a much more expensive server edition which was basically the same, but included IIS, Microsoft's web server. In other words, to legally use Netscape's (or anyone else's) web server on Windows NT, you still had to buy Microsoft's web server.
See also: http://www.landley.net/history/mirror/ms/differences_nt.html