Re: compiling mojo under linux..
Honestly I have no idea. Joseph Hill, who did the initial implementation of the data layer for PostgreSQL contributed the make files.
I compile on Windows with Visual Studio.NET and only deploy on mono though I do hope one day to be able to develop on linux with MonoDevelop I don't think its quite ready for primetime as far as being able to debug web apps.
In VS.NET I change between the different data layers by changing the project reference in the mojoPortal.Business project to point to whatever data layer I'm working with at the moment.
Sorry I can't be of more help, at the current time you really need VS.NET to work with the source code.
If you use the release files you don't need to re-compile.