As of 2007-12-15, using mojoportal from svn trunk r3193 or newer, it is possible to build on Windows using Visual Studio 2005 or 2008 and have the build run on linux using Mono 1.2.6 or newer.
Change the solution to Release build
Right click the Web project in VS Solution Explorer and choose Properties. Add a compiler directive for MONO
Rebuild the solution using Rebuild Solution
After packaging the build, rename the Web.config file to Web.windows.config and rename the Web.mono.config file to Web.config
Delete the Microsoft.Web.Preview.dll from the bin folder
Delete System.Web.Extensions.dll from the bin folder
Delete the file named settings.map.config in the root.
Deploy