Better late than never they say...
yes, you should be able to use trunk on github - fixing the lack of proper tags in the master repo this week so stay tuned.
I added my hand-woven 4.0.0 tools SNAPSHOT to the hibernate3-maven-plugin and experienced the described the Ant issues. I don't think this is a use case you actually test. Why should you..once tools 4.0.0 is out the Maven plugin maintainer(s) have to take of that. IMO there's little hope, though. Never got any feedback to the post I sent to their mailing list.
About autoregistered usertypes, can you show me the code you actually want to have executed ?
We use the Usertype library to map Joda Time data types via Hibernate (it's also JSR-310 compliant). It provides several implementations of org.hibernate.integrator.spi.Integrator. The relevant abstract class is AbstractUserTypeHibernateIntegrator (
autoRegisterUsertypes()). The relevant sub class that provides implementations of getUserTypes() and getCompositeUserTypes() is UserTypeJodaTimeHibernateIntegrator.