Relaks I might be wrong but they publish on their own repository (which can be accessed by Obtanium, or another F-Droid client like Droid-ify, if you don't want to use F-Droid), not on the F-Droid repository, and I have seen that at least one of the Molly versions prompts to self update after being installed via the F-Droid repository. Just saying this as there are issues with F-Droid but this avoids most of them.
The only issue I guess is the fact that multiple app repositories are accessed by F-Droid clients, but as I said you don't need to use them.
I don't speak on behalf of Molly by the way and may be wrong, just thought I would reply with my thoughts
EDIT: oops more knowledgeable people replied before me anyway
It looks like I may have been wrong about the Molly app repo repository versions self updating. Not sure