You really need Visual Studio to use the source code in this project. Also, this is not a beginner project, so I would advise you not to start with this!
You can learn ASP.NET by using the free Web Matrix IDE at
www.asp.net, or you might try the free Sharp Develop IDE if you want to learn Windows programming (as opposed to web programming) with C#.
Either way, though, those other IDEs are not suitable for this particular project.
Eric