I am working on the integration of the Claim plugin with Hudson Tray Tracker (http://code.google.com/p/hudson-tray-tracker/). I want to be able to post claims from Hudson Tray Tracker but the HTTP authentication is ignored in this case. This results in "This build was claimed by anonymous".

What Hudson Tray Tracker does is a POST with Basic HTTP authentication. You can achieve the same with:

curl -v -u username:password -d "json=%7B%22reason%22%3A+%22Some+reason%22%2C+%22sticky%22%3A+true%7D" http://hudson.idm.fr/job/Maven%20test/32/claim/claim

You can see screenshots of the integration of Claim in HTT here: http://blog.idm.fr/2010/07/hudson-tray-tracker-version-0111.html