For Proof of Participation, we have a federation of nodes that create the blocks. The protocol only lets new people into the federation slowly (and prioritizes those willing to stake the most). We measure the "participation" of nodes by whether they are rebroadcasting transactions and blocks, and we kick out the nodes that aren't doing their job.
So the only similar thing to PoS is that we use stake as a Sybil prevention mechanism. Otherwise, all nodes in the federation have an equal chance to create blocks and equal rewards.
