A new KDE IOSlave enabling easy access to Freenet has been announced by Jay Oliveri in this message to kde-devel.
KDE makes it easy to integrate other projects with its extensible IOSlave architecture. The architecture allows seamless net, file and device access for all KDE applications.
To see the complete list of protocols supported check in kcontrol under Network->Protocols. At the moment there are already more than 35, including http, nntp, audiocd (cd grabbing), imap (mail folders), smb (windows networking), floppy (disk access without mounting), kamera (access to photos in camera). Freenet access is an interesting addition, with hopefully more to come.