The class is a remnant from 5.3->5.4 / Java 5->6 transition.
Right now, it's only used in RegistryImpl to inform the user that JDK 1.5 is outdated und Java 1.6 is required for Tapestry 5.4+.
In relatity, Java 8 is needed, so it makes no longer sense to have the check.
The other method of the class,
createLockForThreadLocalCreation()), isnt used at all in Tapestry itself.
The Dummy related org.apache.tapestry5.ioc.internal.util.DummyLock is deprecated since 5.4
Both classes should be removed, because they don't serve any purpose.
Being in an internal package should make the removal not an issue.