There was a temporary workaround to make the player work after June 30, 2013, but it’s no longer applicable.
After seeing that no direct replacement is available I have created an add-on (jPlayer Jukebox) for jPlayer media library to replicate Yahoo! Media Player functionality.
Please visit dedicated jPlayer Jukebox add-on page for demo, installation and usage information.
Initial version doesn’t support all of the Yahoo! Media Player functionality, features will be gradually added based on feedback from users.