@Water_Flame on 4 Nf3 g5 Black plays comparable to the Fischer Bust and the Bc4 is misplaced here.
I have compiled the critical lines into a small study. In short, on 3 Bc4 black should play Nc6!! and then 4 d4 Nf6! or 4 Nc3 Qh4+! or 4 Nf3 g5!
black is better in all lines in my opinion, 4 d4 being whites best try. The Kings Gambit is still busted. Unfortunately.
Here is the study: