Over the past couple of years Microsoft has been open sourcing some key .NET libraries under the MS-PL or Apache 2 license.

We are tremendously grateful to Microsoft for making these components open source. This has allowed us to distribute this in the past, and we are going to be bundling a lot more of it with Mono 2.8:

In Mono 2.8, the following assemblies and code come from Microsoft:

• Managed Extensibility Framework, a framework to create extensible applications (blogged about their open sourcing).
• The Dynamic Language Runtime is the engine that powers IronPython and IronRuby, but also third party efforts like IronJS and RemObject's Javascript compiler. This lives largely in the System.Core assembly in .NET 4. Some of the code is also used in Mono's version of System.Numerics.
• OData's .NET client (System.Data.Services.Client), I blogged about this here.
• ASP.NET MVC both MVC1 and MVC2.
• Microsoft's AJAX library for use with ASP.NET WebForms.
• Silverlight's Controls, these are used by Moonlight.

With Mono 2.8 we are going to default to the .NET 4.0 profile. So from the list above MEF, the DLR, OData and MVC2 become first class citizens in Mono-land, no longer third-party packages that you needed to install.

Update: as of July 17th 2010, the DLR, IronPython and IronRuby changed their licenses from MS-PL to Apache2.