The fear that someone else might be "better" than you so you're intentionally going to make it impossible for them to even compete is a really dumb argument. Imagine if this was done in sports.
And that seems to have been the whole intention behind this. Make sure no non-GPL backend can be used because god forbid it's better than ours. The shame!
And that seems to have been the whole intention behind this. Make sure no non-GPL backend can be used because god forbid it's better than ours. The shame!