GWT need to have access to the source files to compile them
into Javascript code. If you add the project or the jar file to your
GWT classpath then the Java compiler will not complain if you use the
classes from the included project / jar but the GWT compiler will not
be able to compile them.
To make the Java files available to the GWT compiler you need to
Create a gwt.xml file in the Java project / jar file
which you
want to use - This will instruct the GWT compiler to use
the listed
classes.
Use the included library via the inherit definition
If you are using a jar file you also need to include the
source files in the jar
