It depends on the download package - really, because you do have a choice. But if you get mortbay references in your logs, then it is Jetty.
An Apache-JK2 howto is available at http://www.amitysolutions.com.au/documents/JK2-technote.pdf. Hopefully it will answer most questions you have.
Thanks but the link appears to be dead.
Works for me. Can you get to the site at all?