Attached patch upgrades deps to PMD 4.2.2 (and jaxen 1.1.1,asm 3.1, and backport-util-concurrent 3.1).
Also includes support for the PMD Ant-Task "mimimumPriority" setting with the maven.pmd.minimumpriority property. (Allows you to set the priority at which violations are triggered to fail the build - rather than just any violation.)
And, if interested, I would be willing to join the project to test and commit this sort of stuff on various Maven 1.x plugins (I work for a company that still heavily uses Maven 1.x, though we also use 2.x in some places - a lot of our 1.x plugins are updated where the current released versions are not).
Upgrading pmd has been on our agenda for a while (MPPMD-32) but it was ultimately abandoned because of classloader concerns, see [1] for discussion. Development on m1 and m1 plugins is generally suspended now, unless there is sustained interest from a larger community, I don't think there will be any more releases.
If you want to become a committer you will have to follow the Apache meritocracy rules [2], ie submit a significant number of patches over an extended period of time.
[1] http://www.nabble.com/-m1--PMD-plugin-dependencies-tt14038679.html#a14038679

[2] http://www.apache.org/foundation/how-it-works.html#meritocracy