Open Source math? Well, yes in way I guess it is. Then again, this could just be best described as an Open Source compiler for the .NET platform.
Welcome to .Math, the OpenSource expression compiler for the .NET platform written entirely in C#. Offering speed through compilation of expressions, the library allows for variable handling, an entire function library and the ability to add your own functions.
.Math Sourcecode is available as an OpenSource license on the web at http://workspaces.gotdotnet.com/math. [Get the links]