Theory tells us this is not a sound opening for White. I disagree. It just might not be the best use of the White's opening advantage, especially when the gambit is turned down.
If accepted, however, best play by Black (5 .. d5), careful defence, and patient counter development may be able to achieve slightly better than equality, but on balance, I think it is far better for Black to pass up on that second pawn.
If you accept this Gambit as Black and are unfamiliar with the opening, just know that you have entered a veritable minefield. Those two pawns will soon seem like very small recompense for White's multitude of attacking threats. Just try hanging onto those pawns, and you will soon be beaten. You have to give them back to slow White down.
It is a pity that we don't see enough DGA at master level. Database representation and stats are very thin indeed. As for engine analysis of this opening... well, at the best of times, engines are rather poor at assessing the relative merits of material versus development. And this is especially true in the DGA where there is so much to weigh up.
DGA often turns into a violent blood-letting, but these games are always fascinating to watch and very enjoyable to play.