iphone app downloadable from website

[mg555]

I came across this page Recognition PR - Marketing and public relations consultancy which has an iphone app download on the homepage (bottom right).

Anyone know how they are doing this? You can download it and install it direct from that link. I thought you could only do this with ad-hoc distribution (in which case, wouldn't every device that downloaded it need its UUID adding to the profile before it could be used), or Enterprise distribution (in which case, surely it shouldn't be available as an open download on the site)

Or am I missing something - is their some way of freely distributing an app from a website using some other method?