Simple Mobile apps have been very popular among FOSS enthusiasts. I've personally been using the Gallery, Contacts and the Phone app since a few years now. It's a shame that it has come to this, will be on the lookout for their forks.
All the code is GPLv3 so it will remain FOSS. There's no need to immediately switch to other apps. You can optionally fork then build the apps for yourself.
I was talking about immediately switching. There is enough time to build the apps from source for yourself before they upload their shittified version.
If the next version is close-sourced, that means that it won't be published in the repository that F-Droid follows to build their version. Yeah I think you're safe.
Why do you say that? Unless they completely rewrite the app from scratch it is not even possible to have a closed-source version of the app. That's what the GPLv3 does.
If all the developers of the GPLv3 version agree to relicense their contributions, it's unfortunately possible to close-source further versions of the source code. Does somebody know if Simple Apps accepted external contributions?
There's like 100-200+ individual contributors to each of the apps. Practically impossible for everyone to agree to relicense especially considering the community reaction to the sale.