http://chatlogs.musicbrainz.org/musicbrainz-devel/2013/2013-07/2013-07-08.html

Especially given our updated list of supported browsers and the promoting-insecure-practices angle of JSONP support, as well as the requirement we continue supporting this if we decide to enable it, we've decided in the dev meeting to wontfix this.

Not all of our supported browsers support CORS; specifically, it's supported by:

Gecko 1.9.1 (Firefox 3.5, SeaMonkey 2.0) and above. (we support FIrefox 11+, thus we're fine)
WebKit (Initial revision uncertain, Safari 4 and above, Google Chrome 3 and above, possibly earlier) (we support chrome 18+ and safari 5.1+, thus fine)
MSHTML/Trident 4.0 (Internet Explorer 8) provides partial support via the XDomainRequest object. (we support 8+, so we... well, other than IE being silly we're fine)
Presto-based browsers (Opera) implement CORS as of Opera 12.00 and Opera Mobile 12, but not Opera Mini. (we support 10+ – i.e., at least two versions of opera we support don't support CORS)

(ref: wikipedia page on CORS)

JSONP is a hack which was necessary in the past when browsers did not support Cross-origin resource sharing. We support CORS, I don't think there is any added value in supporting JSONP.

So, I suggest we close this as WONTFIX. If you disagree, please join our weekly development meetings [1] on IRC to advocate for this change.

[1] http://wiki.musicbrainz.org/Development_Chat

Agreed to leave intentionally unscheduled by scheduling meeting http://chatlogs.musicbrainz.org/musicbrainz-devel/2012/2012-07/2012-07-24.html