Beginning in 2001, [[Microsoft]] announced they would release part of the [[.NET frameworkFramework]] infrastructure source code in [[Shared source]] through [[C Sharp (programming language)#Standardization|ECMA]], as part of the [[C Sharp (programming language)|C#]] and [[Common Language Infrastructure|CLI]] standardization process.<ref>{{cite web | url= http://ondotnet.com/pub/a/dotnet/2001/06/27/dotnet.html | title=Microsoft Plans Shared Source .NET | publisher= On .Net | quote= On Wednesday, Microsoft announced plans to release what amounts to a shared-source version of its .NET infrastructure for Windows and FreeBSD. Specifically, Microsoft says it has been working with the ECMA standards body and will release ECMA versions of the Common Language Infrastructure (CLI), a C# compiler, and an ECMAscript compiler. The CLI is similar to the Java virtual machine, in that it acts as a translator between the .NET infrastructure and other platforms. Program manager Dave Stutz says Redmond will work with Corel to develop the code | first1 =David | last1 = Sims | author2-link = Tim O'Reilly | first2 = Timonthy ‘Tim’ | last2 = O'Reilly | author3-link = Rael Dornfest | first3 = Rael | last3 = Dornfest | date = 2001-06-27 | accessdate = 2009-09-27}}</ref>
In March 2002, Microsoft released version 1.0 of the '''Shared Source Common Language Infrastructure''', also called '''Rotor'''.<ref>{{cite web | url= http://ondotnet.com/pub/a/dotnet/2002/03/04/rotor.html | title = Uncovering Rotor — A Shared Source CLI | publisher = On .Net | first = Brian | last = Jepson | date = 2002-03-04 | accessdate = 2009-09-27}}</ref> The Shared Source CLI was initially pre-configured to run on [[Microsoft Windows|Windows]], but could also be built on [[FreeBSD]] (version 4.7 or newer), and [[Mac OS X]] 10.2. It was designed such that the only thing that needed to be customized to port the Shared Source CLI to a different platform was a thin [[Abstraction layer|Platform Abstraction Layer]] (PAL).
