It is not a problem at all if your business model isn't solidly based on selling thin air and if you are not planning to suddenly rip off your userbase in the future.
This ripoff can be in the shape of Telegram Premium, but it also can be in the shape of Atomic Wallet, if you know what I mean.
Honest and large FOSS projects often offer paid support and other bonuses that don't hamper the trust in the main codebase.