Miguel de Icaza, lead of the Mono project (opensource CLR) on the new Dynamic Language Runtime:
Binaries of the DLR were released today as part of Silverlight 1.1, and the source code was included with IronPython 2.0 (also released today).
The release for the DLR is done under the terms of the Microsoft Permissive License (MsPL) which is by all means an open source license. This means that we can use and distribute the DLR as part of Mono without having to build it from scratch. A brilliant move by Microsoft.