MediaWiki history

Wikimedia and MediaWiki developed organically (read: chaotically). Initially there was just Wikipedia, and it ran on the basis of UseMod wiki. In fact, in the very first weeks, Wikipedia even used CamelCase (see en:CamelCase). This would later be known as Phase 1 of the script. Some Wikipedias would continue to run the UseMod software until December 2003, including the large Italian Wikipedia, because the differences between the databases made conversion difficult (see Wikipedia software upgrade status).

In January 2002, Wikipedia was switched to a completely new wiki engine in PHP, developed by Magnus Manske specifically for Wikipedia, to offer more functionality and build upon a scalable infrastructure (i.e. a MySQL database). This became known as the Phase II software. It was also commonly referred to as "the PHP script". The last version of the Phase II branch is available here:
 * README
 * Browse the code in CVS

A fork of the Spanish Wikipedia, Enciclopedia Libre, continued to run Phase II until early 2004.

More translations and new projects like Wiktionary were set up. In response to growing scalability concerns, Lee Daniel Crocker rewrote the software based on the Phase II code. This was, logically, called the Phase III software, but it still had no name of its own. Instead, it was sometimes called the "new codebase", after the CVS module where the code was stored.

In the coming months, Brion Vibber effectively took over as lead developer and release manager of the software. The code is now maintained by a large and active group of developers. LDC reorganized the code a bit in April 2003 by LDC and moved it into the new CVS module "phase3", which is still the module where the code currently resides.

After the Wikimedia foundation was announced on June 20, 2003, the name "MediaWiki" was coined by Wikipedia contributor Daniel Mayer as a play on Wikimedia and the name change was implemented by developer Erik Möller a couple of months later. Daniel registered the mediawiki.org domain.

There are no immediate plans for a Phase IV of the software. Instead, MediaWiki development now happens in smaller steps: see MediaWiki roadmap.