The same day, Microsoft published .Net Framework 2.0 and ASP.Net 2.0, DotNetNuke 4.0 was released. DotNetnuke 4.0 is an 1:1 port of DotNetNuke 3.2 and is developed simultaneously. Versions are siimilar as follows:
DotNetNuke 3.2.x ~ DotNetNuke 4.0.x
DotNetNuke 3.3.x ~ DotNetNuke 4.1.x
Modules, Providers and Skins for DotNetNuke 3 are usually working under DotNetNuke 4 without lomitation (but not vice versa).
DotNetNuke 3.3/4.3 introduced a new, extensible membership provider and secure file system. At Version 3.3.7, DotNetNuke 3 developement was terminated.
DotNetNuke release 4.4 focused on performce increasement.
DotNetNuke 4.5 included AJAX.Net support into the application framework.