No response from iTMS affiliates program on the POST problem. Total brick wall trying to contact a human there, but I’m not ready to give up on being an iTMS partner while iPod is king. Finally solved it with a workaround (which I hate): If user voted on the previous lyric, the vote is processed, then, rather than displaying the rest of the output immediately, the browser is invisibly directed to the next page through a location header rather than POST. User still gets the same page she would otherwise, but links to iTMS now work without throwing a confusing “Re-POST?” dialog in the browser.
Love how trivial it is to create links to artists in Rhapsody, e.g.: http://www.rhapsody.com/PatsyCline — which means I can auto-generate the URLs. So what was a 10-hour database population job for iTMS was a 5-minute job with Rhapsody. Hey Apple: Cluetrain!