Open Source .NET This document introduces IronPython, the Dynamic Language Runtime (DLR), and how they enable open source development using .NET. IronPython allows Python code to run on .NET and take advantage of .NET libraries. The DLR allows multiple dynamic languages like Python, Ruby, and Lua to run on .NET. A demo is shown embedding IronPython in C#. Benefits include prototyping, rules engines, plugins, and cross-platform development using Mono.