I am looking for a simple application to track task in a small team environment, the requirements are quite simple.

• Assign a task to a user
• Manage tasks, edit (if possible with history)
• Notification by email
• Web GUI, preferably written in java (deployable on tomcat/jboss/Geronimo) although a php or cgi solution would work as well. Nothing fancy really, and I could probably roll my own pretty fast (by example leveraging appfuse or equinox), but I rather reuse some existing piece of software.
  Any suggestions??