the KDevelop mailing lists have moved to the KDE infrastructure. See the news on kdevelop.org and head over to the mailing lists site to find the locations of the new mailing lists.
Note: No users where migrated, thus you have to register again! To do that, sent an email to email@example.com and/or firstname.lastname@example.org with the subject
Cheers, and again many thanks to the KDE sysadmin crew!