Although the SSCLI is not suitable for commercial use due to its license, it does make it possible for programmers to examine the implementation details of many .NET libraries and to create modified CLI versions.
[1] In March 2002, Microsoft released version 1.0 of the Shared Source Common Language Infrastructure, also called Rotor.
[2] The Shared Source CLI was initially pre-configured to run on Windows, but could also be built on FreeBSD (version 4.7 or newer), and Mac OS X 10.2.
[8] Later versions of .NET, originally known as .NET Core and now referred to simply as .NET, have been open sourced under the more permissive MIT license.
This license allows modifications and redistribution of the code for personal or academic usages, but they can't be used for commercial products.