Hasn't it always been referenced in every set of accounts as an interest-free loan? If so then surely they can't go back on that, that would be crazy.
Fucking wish I didn't have to wonder so much about accounting these days, it's boring and confusing.
I'm sure they mentioned at one of the fans forum about the SD advertising being ok as Ashley wasn't charging interest on the loans. That's probably as close to an official acknowledgement that you'll get.
edit:
http://www.thenorthernecho.co.uk/sport/11039090._Why_doesn_t_Mike_Ashley_sell_Newcastle_United___Here_s_one_compelling_reason____/?ref=var_0