Microsoft’s .NET is coming to VMware’s Cloud Foundry project, an effort to create a standard open source platform for building “developer clouds.”

On Monday, the Bellevue, Washington-based Tier 3 announced that it will contribute code to the project that allows .NET applications to run atop VMware’s platform. At the moment, Cloud Foundry is limited to Java, other JVM frameworks, Ruby on Rails, Sinatra, Node.js, and PHP.

In essence, Cloud Foundry is a way for developers to build web applications, deploy them to the net, and readily scale them to additional users — without having to worry about the computing infrastructure that runs beneath them. “It lets you worry about the app,” project leader Derek Collison recently told Wired, “and not virtual machines or what operating system they’re running or all this other stuff.”

VMware offers the platform as an online service at its own CloudFoundry.com. But in open sourcing the project, it hopes to encourage the creation of compatible services.

Microsoft offers a similar developer cloud or platform cloud with Microsoft Azure, while Google offers its App Engine. But neither company has opened sourced the code behind these services. In adding .NET to Cloud Foundry, Tier 3 is providing a new challenge to Azure, which was build around .NET, but also runs languages such as Java and PHP.

Tier 3?s code is known as Iron Foundry, and it’s available on GitHub under an Apache 2.0 licence. In addition to code that handles the .NET applications atop the platform, Tier has also provided a Windows version of Cloud Foundry Explorer or a Visual Studio plugin for the platform.

To ensure that contributors have access to engineering and technical support, Tier 3 says it will lend its engineers to the IronFoundry.org community forums and donate a full test bed environment, consisting of one web server instance and one database instance per developer for 90 days. You can grab a test bed merely by providing an email address, setting up a password, and agreeing to a EULA.

“As enterprises accelerate the deployment of their mission-critical applications to the cloud, the need for a .NET-based Cloud Foundry PaaS in the marketplace was acute,” read a canned statement from Jared Wray, Tier 3?s chief technology officer.

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