log4j  is a dependency coming from 

 +- org.acegisecurity:acegi-security:jar:1.0.7:provided
 | +- org.springframework:spring-jdbc:jar:1.2.9:provided
 | | - org.springframework:spring-dao:jar:1.2.9:provided
 | +- oro:oro:jar:2.0.8:provided
 | - log4j:log4j:jar:1.2.17:provided

slf4j is used directly by Jenkins.

even though the scope is provided this causes duplicate entries on the compile classpath which causes issues when you are generating annimal sniffer annotations for example.

[ERROR] Failed to execute goal org.codehaus.mojo:animal-sniffer-maven-plugin:1.18:build (build) on project operations-center-jenkins-signature: A type incompatibility occurred while executing org.codehaus.mojo:animal-sniffer-maven-plugin:1.18:build: Cannot merger class org/apache/log4j/RollingFileAppender as it has changed superclass: 

the transitive dependency on log4j should be excluded