DLR is a framework for implementing dynamic languages on top of the .NET Framework. It is used as the basis for IronPython2 and IronPython3. It is licensed under the permissive Apache 2.0 license.
IronPython2 is an implementation of the Python programming language running on the .NET Framework. IronPython2 implements compatibility with Python 2.x. It is licensed under the permissive Apache 2.0 license.
IronPython3 is an implementation of the Python programming language running on the .NET Framework. IronPython3 implements compatibility with Python 3.x. It is licensed under the permissive Apache 2.0 license.
Jim Hugunin created the project and actively contributed to it up until Version 1.0 which was released on September 5, 2006. Thereafter, it was maintained by a small team at Microsoft until the 2.7 Beta 1 release; Microsoft stopped internal development of IronPython in late 2010. IronPython 2.0 was released on December 10, 2008. The DLR, IronPython2 and IronPython3 are maintained by Alex Earl and countless other contributors!