Regarding DUUL

So this new site has popped up called duulnow and supposedly it's a site that hosts contests every month/week/day and you can compete with other players on the site and the rewards are varying amounts of RP depending on the challenge and your place in the contest. It asks you to create an account and link your LoL account via changing the name of one of your rune pages (similar to one of those third party softwares that let you check your stats and other peoples stats in game etc etc). It doesn't ask you for any of your league personal info except the summoner name so all in all it SEEMS safe, but of course I am leery about any site where you can basically get "free rp" even though on this site you have to compete for it. Is there any way this could somehow install a keylogger or something of the sort that could compromise your personal info? Or is this semi "legit". I tried playing a couple games to see if the info updated on the site and recorded my progress and it DOES look as though it is following my match history. I haven't finished any of the contests yet to see if there are actually legitimate rewards but will report back if I find out anything else new. Also one other thing, is this even legal? By either actual law or League of Legends rules? If not I would like to know so I can back out and cease using the site I just wanted to make this post for awareness and to shed some light on this.