Read further: "But if the computer buyer makes a donation to software development himself, he can take a credit against the tax. He can donate to the project of his own choosing".

I think there would be much less offense taken to this "tax" if we could pay the $5 to the artist of our choosing and get the same benefits.

So the buyer donates to his friend, and his friend donates to him, and effectively no one ends up paying the computer tax.