When I run-war a trivial application with 1 controller that outputs "hello", I see:
Running Grails application..
SLF4J: Class path contains multiple SLF4J bindings.
SLF4J: Found binding in [jar:file:/Users/marc/.ivy2/cache/org.slf4j/slf4j-log4j12/jars/slf4j-log4j12-1.5.8.jar!/org/slf4j/impl/StaticLoggerBinder.class]
SLF4J: Found binding in [jar:file:/Users/marc/.grails/1.2.0/projects/RunWarTest/war/WEB-INF/lib/slf4j-log4j12-1.5.8.jar!/org/slf4j/impl/StaticLoggerBinder.class]
SLF4J: See http://www.slf4j.org/codes.html#multiple_bindings for an explanation.
Server running. Browse to http://localhost:8080/RunWarTest