https://logging.apache.org/log4cxx/

• currently undergoing Incubation - there is no official release
• update/bug fixes once in the past 12 years, last release was 2008
• user can select different LogLevels – TRACE, DEBUG, INFO, WARN, ERROR, and FATAL
• hierarchical Loggers
• it is possible to log asynchronously
• supports multiple appenders
• user can select to enabled or disabled the logger
• log can be sent to different and multiple output targets
• user selected output formats
• well documented
• is licensed under the Apache License, an open source license certified by the Open Source Initiative

https://sourceforge.net/projects/log4cplus/

• updates/bug fixes - last release was Jan. 2016
• user can select select different LogLevels – TRACE, DEBUG, INFO, WARN, ERROR, and FATAL hierarchical Loggers
• supports multi–threaded applications but is not safe to be used from asynchronous signals’ handlers
• user selected output format: SimpleLayout, PatternLayout, TTCCLayout
• supports multiple loggers
• not well documented

• is licensed under the Apache License V2.0

https://sourceforge.net/projects/log4cpp/

• bug fixes are about once a year, last release was April 2015
• supports multi-threaded applications •no clear documentation exist
• is licensed under the GNU Lesser General Public License (LGPL) as of version 0.2.1, before that have been released under the GPL.