Has the license for the Microsoft Reference Source code changed?


The .NET reference source code for Version 4.5.x at the Microsoft Reference Source web site used to be licensed under the restrictive Microsoft Reference License (Ms-RSL). It is my understanding that parts of it were published under the MIT license at GitHub with the rest remaining under the (Ms-RSL).

Today if I click on the “License” menu item at the Reference Source web site I am shown the MIT license. This then brings me to my question:

Can I now freely use all of the Reference Source code for anything I want to?

Or only the code currently available on the GitHub web site?

In particular I would like to know if I could copy code from the implementation of a WPF control and use it in my commercial software code.

Links to official statements on this matter would be appreciated.


Thanks Michael.

The Reference Source website did temporarily have the wrong license showing yesterday in error. It should have been showing MS-RSL rather than MIT and I just confirmed it is showing MS-RSL again now.

A subset of that code is re-licensed by Microsoft under the MIT in the ReferenceSource GitHub repo (basically the code that is coming out of the .NET Framework and being implemented in .NET Core as a proper open source project). If you have a request for a class or set of classes from the .NET Framework Reference Source that you want bringing over into the referencesource GitHub repo under the MIT license then post back with more information and we can ask the relevant folks. There is a non-trivial amount of work involved in getting some of the code released under the MIT license which is why we haven’t done it with the whole lot (we prefered to have some of it available and work incrementally rather than wait for all of it)

You might want to also check out the following page for an updated list of what is and what isn’t open source yet:

Sorry for the confusion.


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