OK, I got it to run with <ejb-local-ref> using the sample from
http://cwiki.apache.org/GMOxDOC20/very-simple-session-ejb-example.html(which does contain a web.xml)
<ejb-local-ref>
<ejb-ref-name>ejb/Secured3</ejb-ref-name>
<ejb-ref-type>Session</ejb-ref-type>
<local>ejb3.Secured3</local>
</ejb-local-ref>
context = new InitialContext();
Secured3 secured3 = (Secured3) context.lookup("java:comp/env/ejb/Secured3");
I also needed a sys:dependency from geronimo-web.xml to openejb-jar.xml to make the remote interface known to the JSP (this is missing in the above sample).
First I simply included the ejb.jar into WEB-INF/lib, but this results in ClassCastException on JNDI lookup (I guess because the Remote interface in JNDI is from a different (the ejb) classloader than the cast target which is from the web application).
Thanks,
Juergen