"The whole idea of F-Droid is that every piece of software they offer or use - from the app library right down to the code forge they develop on - has full source code available. So this moonshot project could start as computer science research that just replicates their methodology, to see if that creates the same results."
The main advantage of Replicant over other GNU/Linux distributions certified by the FSF is that it can run Android applications, but that is only relevant if there are 100% free software Android applications.
Somewhat recently we found out that it was no longer possible to know if Android applications shipped by F-Droid are really free, as F-Droid now uses the nonfree Google SDK to build the applications. As such we don’t know if they build with another SDK on FSF certified GNU/Linux distributions. We want to help fix that to make sure the solution really suits our needs.
I don't have a direct link to further details, but GNUtoo is trustworthy.
It's the truth; https://f-droid.org/docs/Installing_the_Server_and_Repo_Tools/ "To build apps using F-Droid, Java and the whole Android SDK must be installed. This process is currently only developed on GNU/Linux, but we’d love patches getting it working on macOS and Windows. If you only want to make F-Droid repositories of APK files that you already have or don’t know what this means, then you can skip this section.
In order to build Android apps with the fdroidserver toolchain, Java, the Android SDK, and some other essential tools must be installed. Only parts of the Android SDK are available in Debian, so the Android SDK must be installed manually, as well as the packages that it requires (the Android SDK tools include some 32-bit binaries, so even 64-bit systems need these i386 library packages). The F-Droid tools use the Android SDK to build and inspect apps, so you must have the Android SDK installed and setup before using fdroidserver."
"The Android SDK is made available by Google under a proprietary license. Within that, the essential build tools, SDK platforms, support library and some other components are under the Apache license and source code is provided."
@Suiseiseki > F-Droid now uses the nonfree Google SDK to build the applications
I see no link in this blog post to a primary source proving this claim, and it seems extraordinarily unlikely. Because of the Sagan Standard, I consider it FUD until proven otherwise.