This website is actually rendered from the Wiki contents that you can edit.
When viewing a page on the static HTML website you can click on the edit link (bottom of the page) and you can edit the page.
Other useful Site links are
Note that it takes a little while to update the Apache site at http://activemq.apache.org/
due to caching. Though this site usually updates quickly: http://cwiki.apache.org/ACTIVEMQ/