org.jboss.logging.LoggerProviders tests for the existence of org.apache.log4j.LogManager and if it discovers it assumes Log4j is in use. This is incorrect in the scenario where log4j events are routed to slf4j for eventual routing to another logging engine (a very common use case). This engine may be Logback, but may not. Therefore, the test for whether slf4j is in use is not whether Logback is in the classpath (Logback is AN implementation of slf4j, not THE implementation...), but whether org.slf4j.impl.StaticLoggerBinder is. There should be no attempt to detect Logback itself. JBoss Logging cannot tell through simply loading org.apache.log4j.LogManager whether this class is provided by log4j or by log4j-over-slf4j so cannot use this class to detect log4j use. To clarify, the logic should be:

1) If org.slf4j.impl.StaticLoggerBinder is available, use slf4j.
2) If org.apache.log4j.LogManager (but not StaticLoggerBinder) is available, use log4j.
3) Otherwise use java.util.logging