James Hartig has published a blog article that outlines the reasoning behind the Grooveshark music streaming service not working on Windows Phone (via HTML5). It's all down to... hold your breath... a bug in Internet Explorer. Who would have thought, eh? According to Hartig, once he looked into the problem (after a number of Windows Phone owners complained that streaming could not be achieved) he came up with the following conclusion.
"It seems that the AJAX calls we were making to our API were failing when they were requested over HTTPS. The Microsoft team states that it is a bug with IE8 that you cannot do AJAX calls through XDomainRequest to HTTPS pages from HTTP pages. They never bothered to fix it for IE9. The simple solution would be to just load the site in HTTPS and make all calls in HTTPS, however that is not possible right now.
We only have 1 call to HTTPS on the site right now, but in the future, users will need to login and perform actions that require HTTPS, so this issue is quite the show-stopper."
So it seems we will not be seeing support for Grooveshark anytime soon, and with the issues they're having with apps on iOS and Android (pressure from record labels), we doubt we'll be seeing an official Windows Phone app anytime soon. We did have Music Shark for a while, but this app doesn't appear to be available.