According to showrunners David Benioff and D.B. Weiss, Bush's likeness is used in "a couple of beheading scenes," but was not intended as a political statement. Rather, "we just had to use whatever head we had around."
Despite their claim that no ulterior motive factored into the display of Bush's decapitated noggin, the spoiler still didn't sit well with some.
Soon after word of the "dragon egg" (credit to io9) got out, Benioff and Weiss released an apologia reiterating that the prop was not intentionally used.
"We can't afford to have these all made from scratch, especially in scenes where we need a lot of them, so we rent them in bulk," the pair said in their statement. "After the scene was already shot, someone pointed out that one of the heads looked like George W. Bush."
They went on to insist that they "meant no disrespect to the former President and apologize if anything we said or did suggested otherwise."
HBO released its own statement saying it was also sorry for this "unacceptable, disrespectful" mistake, and will ensure that it is "removed from any future DVD production."
In other words, the Game of Thrones DVD box set you have in your possession is now a collector's item.