According to this article Drools Flow is not an official JBoss product and so they would not be direct competitors:
I personally do not see them as competing products and for me Drools is and stays mainly a business rules engine. As far as I understood the original intention for Drools Flow was to have a possibility to easily combine small rules to bigger complex ones when a kind of flow control was needed. Correct me if I'm wrong. I don't find the article anymore. :(
I have not really used Drools but from what I have seen in presentations on Slideshare it seems a great product to me. My wish would be a joint effort of the Drools and jBPM team to bring the power of Drools to jBPM. Of course this is already possible right now (see the Camunda presentations on this on Slideshare, unfortunately for you they're all in German, I think) but I would love to see a stronger official-like integration.