It is not advertised as a complete recommender – it is what it says. It does the precomputation phase for slope-one, and produces diffs. It is used as input to the on-line slope-one recommender.
You can use the 'pseudo-distributed' Hadoop recommender to run these slope-one recommenders on Hadoop, on top of the diffs computed by this Hadoop job. That's fairly complete.
You could write a new special-purpose Hadoop-based job to finish the recommender computation too. It could be even better. If you mean you'd like to implement that I can leave this open to track this.