[tanlermin]

Check out dask: http://www.slideshare.net/continuumio

Its free with a permissive license and actively growing.

It is also capable of native HDFS integration, Yarn etc and can do more complex and granular parallel patterns than just map reduce. Also has a API for distributed dataframes and arrays with linear algebra ops.

DISCLAIMER: I don't work for continuum. I just want to see its projects succeed because I was a user will benefit.