I did some research on this for an RSS chapter in Radio UserLand Kick Start, and I think Winer's on solid ground.
UserLand introduced a site syndication format called <scriptingNews> format in 1997, a simple XML dialect for viewing a Web site with different browsers.
In 1999, Netscape offered RSS 0.9, a more complex XML dialect for syndication that used the Resource Description Framework (RDF), an XML standard created by the World Wide Web Consortium to make it easier for software to mine documents for information.
By introducing RSS, Netscape wanted to encourage sites to offer headlines to their own pages that could be viewed by users of the My Netscape personal portal service.
Later that year, Netscape dropped RDF from RSS, releasing a new version numbered 0.91 that adopted elements of <scriptingNews> format:
We're trying to move towards a more standard format, and to this end we have included several tags from the popular <scriptingNews> format. ...
RDF references removed. RSS was originally conceived as a metadata format providing a summary of a website. Two things have become clear: the first is that providers want more of a syndication format than a metadata format. The structure of an RDF file is very precise and must conform to the RDF data model in order to be valid. This is not easily human-understandable and can make it difficult to create useful RDF files. The second is that few tools are available for RDF generation, validation and processing. For these reasons, we have decided to go with a standard XML approach.
Because some of UserLand's syndication format was adopted in the first widely used version of RSS, it's fair to credit both companies with creating the protocol.
While I'm opening up this can of worms, Netscape's decision to dump RDF from RSS in July 1999 is the best reason why RSS 1.0 should've been called XRSS, RSS/RDF, or anything other than RSS when it was released in December 2000.
When the RSS-DEV Working Group reinstated RDF from an obsolete version of RSS, it represented a significant fork away from what the protocol's creators had been doing for 18 months with a standard that was well-established and popular.
Their decision to extend RSS with a backwards-incompatible RDF format and call it RSS 1.0 -- against the wishes of UserLand -- continues to confuse people who are thinking of adopting RSS.