It must be interesting to know the version of an osworkflow.jar.
So, while creating the jar in the ant script :

Index: build.xml
===================================================================
RCS file: /cvs/osworkflow/build.xml,v
retrieving revision 1.45
diff -r1.45 build.xml
197a198,202
> <manifest>
> <attribute name="Implementation-Title" value="OSWorkflow"/>
> <attribute name="Implementation-Version" value="${version}"/>
> <attribute name="Implementation-Vendor" value="OpenSymphony"/>
> </manifest>