There has been multiplayer since the beginning of time (2001 when Original War was released). Until v1.09 you could only do multiplayer if you knew your opponents IP address or if you used Game Spy Arcade, 1.09 added Master Server Support. GOG's version of Original War has always had Master Server support.
Note that the patches are Official. In 2005 OWSupport got permission (And the source code) to maintain Original War for Altar Interactive (Now Altar Games). Patches from 1.03 onwards were created by OWSupport.
Note: The Master Server only tells you about games which match your Version of Original War. So if someone has 1.10b and you have 1.11.0 then you both will not see each others games. Only if both people have the same version will they see each others games listed.
Post edited July 26, 2011 by Stucuk