I don't think there is such a thing. Someone has to provide the platform so that players can find each other and compete against each other (a matchmaking system, so to speak). This would then also be the "owner" of the casino and would have to ensure a license, even if the games take place between the players of the platform.
A licence is some sort of trust among gamblers to play on that particular casino but it doesn't imply that they cannot be scam as some of the other casinos have turned out to be scam even after owning a licence but still new legit casinos feel it obligatory to own a licence to increase the reputation and trust of gamblers before entering the market.
-snip-Unfortunately, scam attacks can occur anywhere, neither "classic" large companies are exempt (keyword: Wirecard) nor newer industries such as online casinos.
I also find it very alarming when people blindly trust casinos with licenses. A license unfortunately says absolutely nothing about whether and how a casino is protected against scam attacks itself, nor how "trustworthy" such a casino is.
Yes why should we blindly trust any casino because this crypto market is risky and having an licence doesn't give you symbol of legit casinos in the market but we should be careful at our end.The old gamblers and wise players know this reality and for them license is mere obligation at first step and they play with their insight.If we say of scam then any casino that might seems legit at first end but may be prone to some hacks or scams which have nothing to do with licence.