I could not get this plugin to work using just the plugin and dll file.
Every time I tried to edit a .todo file it gave me the following error:
Cannot create object: Todolist.ToDolistDisplayBinding
When I opened the source and tried to build it, it wouldn't. I had to remove the references to ICSharpCode and ICSharpCode.Sharpdevelop, and add them again. Only then could I build the addin, and then it worked fine in Sharpdevelop.
I don't know if something is wrong with my installation of Sharpdevelop, or if its a problem with the plugin.