Lorien is a chatline largely derived from haven written by Chris Eleveld. In fact, Lorien and haven are closely enough related that they share common sources. Jillian Bolton has maintained the publicly released Lorien distribution since early 1992.
Lorien is a haven --- a chatline with a distinctive user interface. Havens typically use a single server to provide a single chat service, therefore are usually limited to fewer connections than IRC, which uses multiple servers. Another difference from IRC is that haven servers generally do most of the work, whereas IRC clients and IRC servers share the work. Unlike most talkers, havens don't usually have connected rooms which you must navigate. There are some notable exceptions, for example the venerable Hotel California does have rooms, as well as limited multi-server capability.
Havens are generally smaller in both code and source size than IRC servers, MUD servers and talkers. In fact, the smallest haven recorded to date, Minihaven, written by Maikeru Long contains only 2786 lines of C source code. In comparison, Lorien has a seemingly larger 4385 lines. Indeed, while the source sizes indicate that Minihaven is the smaller haven, additional analysis shows clearly that Lorien has a smaller in-memory code size, though it is unclear which server is faster, since there are no published benchmark standards for havens. At the other end of the spectrum is the rather large Hotel California, also by Maikeru Long, which fills an important niche that no other haven to date has challenged: A nearly complete virtual environment with rooms and objects. For this reason, and rightly so, the Hotel remains very popular among haven operators.