Keepass appears to be very secure, because it is open-source and the code is examined by a lot of independent people. Furthermore the database which holds all passwords is stored wherever the user wants it to be. This brings the ability to keep the database offline and secret instead of storing it on a companys servers, like it's the case when you use password managers like LastPass, Dashlane, Keeper etc. For me these are the main advantages of Keepass over commercial password managers.
Because I want to have my passwords with me wherever I go, I feel the need of using a mobile App (iOS) which is capable of handling Keepass databases. Unfortunately these apps aren't official, but unofficial ports by other people. Some of them are even closed source.
What happens if these apps are bad implemented or not maintained continously? Is Keepass still secure when using such third party apps and is there any advantage of open-source if the app is closed source? Is there still a security advantage over a closed source commercial password manager?