Logback is intended as a successor to the popular log4j project, and was designed by log4j's founder, Ceki Gulcu. The basic architecture is sufficiently generic so as to apply under different circumstances. It is divided into three modules. The Core module lays the groundwork for the other two modules, whereas the Classic module can be assimilated to an improved version of log4j. It natively implements the SLF4J API so that you can readily switch back and forth between logback and other logging systems, such as log4j or JDK14 Logging. The Access module integrates with Servlet containers to provide HTTP access log functionality. You can easily build your own modules on top of the Core module.
Mistletoe is a JUnit extension intended for integration testing. In technical terms, it is a JUnit test suite runner presenting the test results via HTTP as a Web page. Mistletoe, when incorporated within an application, will help diagnose integration issues. For example, an application that runs perfectly in the developer's environment may not run properly in the production environment due to configuration errors and connectivity issues. Instead of perusing log files, or looking at stack traces, mistletoe will run a user-specified series of tests and present the results in the form of a Web page served by the application itself. Since the tests are run within the context of the deployed application, given an appropriate test suite, you can home in on integration problems quickly and conveniently.
Syslog compatibility has been tested only with the 1.3 version of syslogd on Linux. Other daemons might behave differently.
UDP is unreliable. Log packets can and often do get lost. Enjoy, Ceki
Stability of v0.6.1
Altough log4j is marked a "development" release, it is failrly stable and is being currently used in a number of projects.