> Okay, the t-shirt for donors is trade-free, because the main product is the software, which should be free for everyone.
I think it'll be more clear if you look at the T-shirt and software as two separate things, one here is trade-free (software which is the same for all), the other one is not trade-free (T-shirt which only donors get).
But that being said, I think this is an edge case where the line becomes a bit blurry. Like asking if a hyena is a cat or a dog