Actually 5..Nc6! is the best BUT my idea wasn't to show the best play in that variation just show that the tempting g4, followed by Qh4 just after it is wrong. Even 5..h5 can be played in oder of defending the pawn.
King's Gambit A Challenge From Ponz

What about 2 f4d5?
1. e4 e5 2. f4 d5 does not give Black any advantage. It is ok but just gives an equal game.

maybe white should try Bc4 instead of h4
That is a great way to lose without any fight (4...Bg7!- no Muzio nonsense).
Best thing is to refute the Muzio, which is not hard.

maybe white should try Bc4 instead of h4
That is a great way to lose without any fight (4...Bg7!- no Muzio nonsense).
Best thing is to refute the Muzio, which is not hard.
Not hard? In 400 years, no one has refuted it yet.

yeah the duoble Muzio... maybe.... actually probably by Qf5 but you still need serious tactical skill and knowledge of games played in that variation in order to survive.

and isn't Nc3 advisable that or d4 seem best.
Please be more clear what position you refer to.

In my analysis I found that 4... g4 is best.
Disagree on this one. I do not think Black should allow the Muzio Gambit.

In my analysis I found that 4... g4 is best.
Disagree on this one. I do not think Black should allow the Muzio Gambit.
One of the few things that's been said so far that I agree with :). Black has a better option after 4.Bc4: the Hanstein Gambit.

Fiinally a draw game! Luft Waffles 1/2 ponz111 1/2
However, for fun I thought I would try 1. e4 e5 2. f4 exf4 3. Nf3 d5
rather than the 3. Nf3 g5 of the other games. So here it is and I am sure Luft Waffles will post comments on this game.
I would slightly dissagree with the line you posted Arkhimeedes, after Ne5 in you subvariation, d6 works well as it takes the g4 square from the white queen regardless, puts the knight to question, and offers a slight advantage to black as now Qh4+is possible.