Sorry to hear you were burned like that. But we have plenty of customers — including large musical organizations — who use Soundslice. They either work out the licensing agreements with publishers or focus on material that they don't have to license.
(I see in your HN bio that you're a Django user — thanks for using it!)
I certainly hope you didn't perceive my comment as negative towards Soundslice. It's sometimes a bit frustrating to see all the possibilities of technology without being able to use them, just due to the intellectual rights maze.
Happy to hear that you're experiencing success in many places. Soundslice looks like a wonderful educational tool!
(I see in your HN bio that you're a Django user — thanks for using it!)