Symptoms:

When try to start the bwagent it failed with below error message
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C:\TIBCO\bw\6.3\bin>bwagent startagent -config C:\TIBCO\bw\6.3\config\bwagent.ini
TIBCO ActiveMatrix BusinessWorks version 6.3.5, build V17, 2017-02-02
SLF4J: Class path contains multiple SLF4J bindings.
SLF4J: Found binding in [jar:file:/C:/TIBCO/bw/6.3/system/shared/com.tibco.tpcl.logback_1.1.0.001/logback-classic-1.0.13.jar!/org/slf4j/impl/StaticLoggerBinder.class]
SLF4J: Found binding in [jar:file:/C:/TIBCO/ems/8.3/lib/slf4j-simple-1.5.2.jar!/org/slf4j/impl/StaticLoggerBinder.class]
SLF4J: See http://www.slf4j.org/codes.html#multiple_bindings for an explanation.
SLF4J: Actual binding is of type [ch.qos.logback.classic.util.ContextSelectorStaticBinder]

C:\TIBCO\bw\6.3\bin>
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Cause:

When you have multiple versions of slf4j jars available in class-path of bwagent, it will create a conflict of version and class and that leads to problem mentioned above.
Installing multiple versions of product in same TIBCO_HOME and updating the .tra file lib path incorrect way leads you to such situation.

bwagent failed to start with error SLF4J: Class path contains multiple SLF4J bindings

All

Remove the older version of slf4j.jar from classpath.

In above case should remove the 'slf4j-simple-1.5.2.jar' from specified location.

Make sure that you should have only one instance or version of slf4j.jar loaded into class-path. Check the bwagent .tra file to check whether other version slf4j.jar instances are getting loaded. If there is any entry of path pointing to other product slf4j.jar then remove it.