Microsoft has posted the source code for MSBuild on GitHub and made the tool available under an open source license. The application building platform is integrated into Visual Studio, but this new release will eventually allow developers to use MSBuild in environments that are not running Visual Studio. Microsoft says it also plans to port MSBuild to Linux and OS X.
Reversing its long history of animosity for the open source community, Microsoft has recently embarked on a project to release much of its .NET development platform tools under open source licenses. This latest release is part of that larger effort.