On the day of Joomla! 1.5.17 release, there was an article posted by Sam Moffatt, a member of the Joomla! Production Working Group Leadership Team, attraced some attention from Joomla! users and started interesting debates. At the center of this small controversy is the article "Microsoft signs the Joomla! Contributor Agreement."
In the article Sam revealed Microsoft had contributed some codes to Joomla! project and had signed the JCA (Joomla! Contributor Agreement). Those codes have been incorporated into the development trunk of Joomla! 1.6.
According to Sam's account, apparently the relationship started when Joomla! developers worked with Microsoft to create a Joomla! package for Web Platform Installer for easy installation on Windows machines. During the process, Microsoft provided test environments and worked with Joomla! developers to solve some long standing bugs affecting compatibility with IIS. Don from Microsoft IIS Team also donated WinCache integration code to Joomla! for better performance under IIS.
Joomla! Team apparently sees this as a welcome development because it helps Joomla! work better with Microsoft's IIS. Yet, the feeling is not universal. Some Joomla! users just don't trust Microsoft and think there must be an ulterior motive for them to contribute into an open source project.
To analysize the situation, we should first ask what the common factors that bring Microsoft to Joomla! Project may be. Joomla! is written in PHP, stores data in MySQL exclusively, can be deployed on a HTTP server with reasonable PHP support. Where is Microsoft in this picture?
It is extremely unlikely they can influence Joomla! Project to switch from PHP to, say, C#. That would constitute a complete rewrite and a new project. It is also unlikely they can push Microsoft SQL Server onto Joomla! If they want Joomla! to use SQL Server as database server, more probable senario is to make Joomla! database neutral. In that case, it would benefit not only Microsoft but also other database vendors and the general Joomla! community. However, I don't see any reason for Microsoft to devote its resources to undertake such a task.
Therefore, it all comes down to making IIS a viable HTTP server platform to host various Web applications. By helping Joomla! run more smoothly on IIS, Microsoft can attract a broader user base. Otherwise, many of Joomla! users will go with the usual server setup with Apache as the HTTP server. Now many compatibility issues with IIS have been solved, and performance on IIS has been improved. Joomla! users can have a choice to deploy Joomla! on Windows platform with IIS.
So Microsoft's contribution to Joomla! is a pure business decision. It is a quick and easy way to expand market share of IIS and Windows platform. Joomla! Project actually benefits from this move albeit not majorly.