Update, 19 March 2021: My Sydney colleague, Andrew Bailey, drew my attention to Longjing Pty Ltd v Perpetual Nominees Ltd  NSWSC 1690 at ff, which is to similar effect.
Original post: In Carter v Mehmet  NSWCA 32, the Court granted the respondents’ security for costs application in part because the appellant’s solicitors had much to gain from the appeal’s success and had agreed to do it no win no fee, and so were creditors associated with the proceeding, but the appellant had not proven that the solicitors could not contribute funds in order to provide security. Since it was not suggested that they could not provide funds to enable the appellant to give security in the order of scores of thousands of dollars (though there was evidence that they would not do so), it could not be said that the appeal would be stultified by virtue of the inability of the appellant and those who stood behind him to provide the security.
If you are a lawyer whose fees are unpaid from round one, consider very carefully whether you agree to do the appeal no win no fee, as opposed to entering into an orthodox retainer in the knowledge that payment may be difficult unless the appeal succeeds. If you are an impecunious appellant in that situation, think even harder about accepting or proposing such a retainer, since — good as it sounds — it may effectively preclude you from pursuing the appeal.