It's taken from www.codeplex.com, an open source project repository built by Microsoft a few years ago that has now expanded to host over 10,000 open source projects built by individual developers as well as roughly 500 by Microsoft employees. The "code" part of the name refers to the source code which is the substance of an open source project. The idea behind "plex", like metroplex or building complex is that it's a commons which serves a wide range of individuals.
The CodePlex Foundation (www.codeplex.org)
is intended to serve a wide range of projects, regardless of platform or
technology base, to enable the exchange of code and understanding among
software companies and open source communities.
Many people benefit from open source software, but a small number of
people contribute back. It seems to us
that software companies should be in a very good position to contribute back
based on employee skills and the benefit that these companies derive from
specific open source projects, but in our experience there are a variety of
obstacles that prevent or reduce contribution.
These range from development culture to copyright and patent licensing
We are working with the leaders of other foundations, including the Apache Software Foundation and the Eclipse Foundation, to ensure that the CodePlex Foundation is a useful complement and enables community-based open source projects to expand their reach through increased contributions from software companies. We are also receiving a great deal of thoughtful input (including Andy Updegrove's article and the community input on our Google Group). There's a long way to go - this really is a brand-new startup and we are clearly in the alpha release - but from what I've seen I'm very optimistic that we can provide value to open source community projects.