Gambling is something that has to do with staking money for a chance to participate in a gambling game but in the situation addressed by the OP, we can consider it to be gambling because it's a promotion provided by super sport and gambling website in order to have more customers on their platform. It's just like giving back to the community.
The occasion is indeed gambling , but the bettor ? can we consider them as Gambler in that way when they did not even put a single cent to gamble?
this is a never ending debate I believe unless will be answered directly by those who are involved and admit if they are gambler or not.
this can be handled by not gambler that only wants to try their luck as it is a freebet.
I never participated in an event and this is the first I will hear about. I did some few research about the event yesterday it is totally free as stated by the OP but the longevity of it is something I don't know but the event seems to be hosted weekly and the lucky winner will be awarded the prize for that week.