DotGNU is a decommissioned[1] part of the GNU Project that started in January 2001 and aimed to provide a free software replacement for Microsoft's .NET Framework.

The main goal of the DotGNU project code base was to provide a class library that is 100% Common Language Specification (CLS) compliant.

DotGNU Portable.NET, an implementation of the ECMA-335 Common Language Infrastructure (CLI), includes software to compile and run Visual Basic .NET, C#, and C applications that use the .NET base class libraries, XML, and Windows Forms.

[8][clarification needed] DotGNU's implementation of those components of the .NET stack not submitted to the ECMA for standardization has been the source of patent violation concerns for much of the life of the project.

However, the .NET Micro Framework is a reimplementation of the CLR and limited subset of the base class libraries meant for use on embedded devices.