Spoofing useragent works. From the look of it, it's a nginx-generated 403, which probably means they hardcoded their nginx config to block web clients they don't consider good webcitizens.

The string they're blocking isn't [Ll]ynx, it's libwww. Which Lynx has in its user agent string. They're not blocking wget or curl.

It's probably a misguided attempt to block custom written bots, maybe a particular one they've had trouble with in the past.