This info is starting to get stale. The plan is to migrate all content into the debian wiki at http://wiki.debian.org/HP/ProLiant. Check there first and come back for additional info if you can't find what you are looking for.
This information is not endorsed by HP and comes without warranty etc. If you break your computer it's not my fault(and you get to keep the pieces).
If you want HP to support Debian you need to contact them and let them know. If you have a sales rep, tell them that you want Debian support and don't take no for an answer. HP will only support Debian when there is sufficient demand to do so. In my personal opinion, based on all the people I've talked to running Debian on ProLiant, if everyone spoke up there would easily be enough demand for HP to justify supporting Debian.