Here. "Apache, the world's most widely deployed Web server, now supports the Microsoft ASP.NET Web services development platform through the Covalent Enterprise Ready Server. This gives enterprise customers who wish to use ASP.NET the freedom to deploy Apache, thus enabling development and operations groups to independently utilize technologies that meet their needs. Covalent has written a white paper describing the technology in more detail."
The Covalent guys have added ASP.NET support to the open source Apache using a lot of elbow grease to map between the differences between the two processing models and the ASP.NET hosting stuff, which Microsoft arguably implemented for just this purpose. If we could get ASP.NET as part of Rotor and Rotor on Linux, you could run ASP.NET-based web servers for free (except for the money you’d pay Covalent for their bits, of course, but since they hired me to help advise them on the implementation of those bits, that works for me : ).