You seem to say those are the only two options. There's clearly a third one: use the API and, if they suddenly enforce the excessively onerous terms, go public

You seem to say those are the only two options. There's clearly a third one: use the API and, if they suddenly enforce the excessively onerous terms, go public in an effort to make them back down from public pressure. This has been shown viable time and again, with App Store rejections and the like. It is obviously high-risk but sometimes worthwhile.