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
Trillian is a proprietary, cross-platform messaging application that supports a wide range of protocols and offers advanced features like encryption and customizable themes, making it suitable for users seeking a rich messaging experience. In contrast, Kopete is an open-source alternative primarily focused on Linux users, offering basic features with plugin support, making it ideal for users who prefer a simple, community-driven solution.