[kuschku]

> With signal, I'm gonna guess it's mainly a; the Play Stores checks and balances are much less invasive than the sort of thing an F-Droid maintainer might check for. (As I understand it, Google Plays checks mostly are anti-exploit and keyword scans.)

It might have been b as well – Signal did keep their server code proprietary for many months to add their custom cryptocurrency to it, and added this cryptocurrency for microtransactions into the app as well. There may be many more features like this planned, some of which F-Droid might oppose.