AdaCore does directly contribute to GNAT which is important.
GNAT was chosen for alire since it is free software: "This work presents a working prototype tailored to the Ada compiler available to open source enthusiasts, GNAT."
Other Ada implementations typically use their own build systems which are different from GNAT's and so they would probably need changes to work with alire.
https://zaguan.unizar.es/record/79726/files/texto_completo.p...
AdaCore does directly contribute to GNAT which is important.
GNAT was chosen for alire since it is free software: "This work presents a working prototype tailored to the Ada compiler available to open source enthusiasts, GNAT."
Other Ada implementations typically use their own build systems which are different from GNAT's and so they would probably need changes to work with alire.