> Various fairly essential libraries maintained by AdaCore are under GPL, so you could not use them for non-GPL software that is distributed.
That's not true, the AdaCore libraries are covered by the Runtime Library Exception of GPL and available on GitHub: https://github.com/adacore
And soon available in the package manager: alire.ada.dev
> The purpose of this Exception is to allow compilation of non-GPL (including proprietary) programs to
use, in this way, the header files and runtime libraries covered by this Exception.