Apache logging services
The Apache Logging Services Project creates and maintains open-source software related to the logging of application behavior and released at no charge to the public.
Log4j 2 is an upgrade to Log4j that provides significant improvements over its predecessor, Log4j 1.x.
A versatile logging framework for PHP. Originally a port of Apache log4j to PHP, it has grown to include various PHP specific features.
Apache log4cxx is a logging framework for C++ patterned after log4j.
A GUI based log viewer. Chainsaw is a companion application to log4j written by members of the log4j development community.
Apache Log4j Audit
Audit logging framework built upon Apache Log4j 2.
Apache Log4j Scala
Scala API for Log4j 2.