The ACIM CE App is a newer type of app known as a Progressive Web App (PWA). PWAs can most simply be described as installable websites. Although they install onto your device, they don’t pose any greater threat to your phone security than using a website would. In fact, the app still runs on your device via Safari (iOS) or Chrome (Android) but the nature of a PWA means you experience it as a ‘native’ app (i.e. just like one you’d get from the App Store or Play Store).
It is possible to make PWAs available via the usual stores, but doing so would limit the reach of this app as not all territories have the same access to apps in that way, and it would also mean updates and bug fixes would take longer to implement. Additionally, donations made via the app (which enable it to be free to use) would be subject to store processing fees. For these reasons we have decided to make it directly available via the internet at this time.
You can read more about PWAs here: https://en.wikipedia.org/wiki/Progressive_web_app.
Please note that you can use the app without downloading it to your phone - go to https://acimce.app and use it in your browser - but it will be more awkward to use and security will be exactly the same. We therefore recommend downloading the app.