I always hate these annoying pop-ups on forums that ask you to download some random stuff before you can view their forums.
There are no pop-up windows that stop you from viewing the forums. Have you actually tried going on the website using your phone to see for yourself?
Besides, if you've ever tried browsing a forum (especially this one) using a phone you'll know that it's horrible. An app is much nicer, I'm thankful it exists.
Even if there was a popup that stopped you from viewing the forums, it wouldn't exactly be "some random stuff" would it? Asking you to buy a shipment of viagra would be "random".