We have begun planning how to open source the code to EtherPad and the underlying AppJet Web Framework. We will continue maintaining new pad creation from the EtherPad home page at least until we have open sourced the code, and work hard to make sure there will be no or minimal service disruption in the future.
I'm a big fan of rt3 ( http://bestpractical.com/rt ).
- Free and open source
- Web, email, and command line interface
- Flexible (I've used for bug tracking, support departments, task and project management, documentation, mailing lists, and more)
- Scalable (I've seen it go beyond 100,000 tickets on an average server with no performance hit)
- Excellent community (mailing lists, wiki, book, contrib section on the site)
- Written in Perl, so its a bit tricky to configure and customize
Give it a try.