Jitsi (previsously called SIP Communicator)is a Java based (using JAIN-SIP) softphone and is cross platform (Mac, Windows and Linux).
It does not seem to support DNS SRV (in spite of using JAIN-SIP, and supposedly it was once fixed http://java.net/jira/browse/JITSI-301). It does also suggest it supports XMPP but not unless you remove xmpp.fqdn and use only xmpp.domain by editing your sipx config.
It has been reported to work. If you have a working example, screenshots and notes on functionality (does RLS work?) with would be appreciated.