I haven't used this, but it seems to do way more than the average person know how to use for an SMS app
Even in the readme, it says:
The technical functionalities of the app are currently not user friendly, which would be updated with the help of PRs and issues. The reason for the lack of user friendliness is solely based on the app aiming to be as customizable as possible. Users should be able to configure the app to their custom cloud servers without being tied into using specific providers.
more or less yes, but im not too familiar with the project. I was just looking for a FOSS keyboard with completion support. I know it has good support for plugins to use latin characters to write characters in other writing systems, like pinyín
Provided that the developer can either remove contributed code or seek copyright licences from every contributor it can be done. Whether this did happen or not is unclear, the developer appears a little arrogant about having written the majority of the code, showing little appreciation towards minor contributors. We cannot tell whether the contributors gave permission for their code to be re-licenced or if their code was removed.
Personally, when contributing to GPL projects I would expect that this kind of thing wouldn't be possible. Using the GPL is a very philosophical choice of licence and is a move to say that you really care about your users