Determine OAS (10.1.3) version

$ORACLE_HOME/OPatch/opatch lsinventory -detail

Get version Oracle Containers for J2EE

cd $ORACLE_HOME/j2ee/home
java -jar oc4j.jar -version

Output:

Oracle Containers for J2EE 10g (10.1.3.5.0) (build 090727.2000.36696)