You can use multiple jars with JSVC using : between them.
For your specific issue the solution would be changing the CLASS_PATH variable to this:
CLASS_PATH=$(pwd)/myapp.jar:$(pwd)/lib/commons-daemon.jar:$(pwd)/lib/other-jars
Alternatively you can include all jars in a directory by using wildcards like this:
CLASS_PATH=$(pwd)/myapp.jar:$(pwd)/lib/*.jar
Hope this helps