When comparing Trillian vs Quassel, the Slant community recommends Quassel for most people. In the question“What are the best IRC clients for Windows?” Quassel is ranked 3rd while Trillian is ranked 15th. The most important reason people chose Quassel is:
Quassal is available for free with source code licensed under GPL and available [here](http://bugs.quassel-irc.org/projects/quassel-irc/repository).
Ranked in these QuestionsQuestion Ranking
Pro In-house server support
You can set up a dedicated server to hold your communications. Great for businesses that want to build their own infrastructure.
Pro Multiple networks in one place
Among them Yahoo!, Facebook, Skype, Google, AIM, ICQ, XMPP, MSN. You can have multiple accounts associated with each service.
Pro Group chat
Trillian to Trillian group chat is available.
Pro Free and open source
Quassal is available for free with source code licensed under GPL and available here.
It's possible for a front-end client or multiple front-end clients to connect to a single core client. This allows setting up an always on-line core that can be accessed from anywhere.
Pro Easy installation on Ubuntu due to the existence of PPA's
Right now Quassel has a PPA maintainer, which allows you to install the stable version or daily versions.
Support for PostgreSQL as database backend and easy to configure for people that know a bit about systems.
Con Supports all dead services.
Con No DCC support
DCC or Direct Client-to-Client protocol allows for private communications between users (without the traffic being routed through servers). Neither chat nor file transfers are supported.