Proprietary solutions will help Spotify succeed: ensuring you have to host with Spotify, sell with Spotify, and get played on Spotify. In return, Spotify ensures that your content will work correctly on all Spotify podcast players, which are rapidly becoming a market leader. It's not a lock-in: you can still offer your listeners a poor, sub-standard experience on other players after all; yet listeners will naturally gravitate to the podcast app which supports the features they want; so Spotify will continue to grow.