A note about the Winboard chronology data
Most of the data below on the number of Winboard engines available is drawn from the hard investigative work of Gunther Simon (with some assistance from me), and he has pain-stakenly attempted to reconstruct the chronology of Winboard engines by release date. If you are interested in the data please go to his excellent site.
Altough the data is not likely to be 100% accurate, it gives a rough idea of the evolution and speed at which the Winboard protocol was adopted. You may find that the figures quoted here differ from those quoted elsewhere or even on my site, but often this is just a result of incomplete information or different methods of recording.
Gunther Simon's data covers only freely released Winboard engines and hence excludes privateware (because it would be impossible to ascertain the exact number of such engines). The data also excludes a small number (about 5) of commercial Winboard engines.
Gunther Simon has drawn his data from various sources chiefly the Newstickers of past and present Winboard engine list maintainers like Frank Quisinsky,Thomas Mayer and the current maintainer Leo Djiksman, lists by Digitalchess etc supplemented by googlegroup searches. However as Frank site's was setup only in Sept 99, there is understandably a lack of information about earlier periods.
Even the relatively well covered periods after 99, may contain inaccuracies because there is a difficult in tracing the exact data where the engine was made available as opposed to merely being known to the maintainer of such lists.
It's also possible to quibbe about whether a totally rewritten Chess engine with a new name by the same author can be considered 2 engines (eg the case of Gromit 2/3 and Zchess/Pharaon and even Gnuchess 4/5 which have different authors).
Lastly, Gunther Simon also had problems dealing with Chess engines that were available in Xboard form long before being ported to Winboard. For some extreme cases like Knightcap it was available in Xboard as much as 3 years earlier before Dann Corbit finally ported it over to Windows in 2001.