I don't like to sound pessimistic, but I don't believe there will be enough incentive for gamblers to buy tickets for such a lottery. There are just too many unknown factors. It might be more interesting if it were some sort of player-versus-player (PvP) game, where competitors battle each other. Just my thought.
The whole app would be decentralized. It means the smart contract is deployed, the source code can be read and it will be verified (green tick mark in network explorers), so basically it will live forever.
Basically to deposit, you just call the deposit function, and there will be a distribute function when the round is over. So let's say even I would create an UI for this app, but for some reason the project is abandoned, it would still live forever on the blockchain. Verified mechanics, everything is handled by smart contract, which is open source and can be verified to rule out malicious code. Actually a contract like this is super simple, so ordinary people could also check if nothing malicious is going on.