Kopete is a multi-protocol, free software instant messaging client released as part of the KDE Software Compilation. Although it can run in numerous environments, it was designed for and integrates with the KDE Plasma Workspaces. Developed by kde.org
License: Open Source
Gajim is a lightweight, open-source XMPP client that excels in supporting multiple accounts and plugins, making it highly customizable for users. On the other hand, Kopete offers broader protocol support and integrates well with the KDE desktop but may not be as feature-rich outside that environment.