I believe this is the Englund Gambit. How closely related it is to the more popular Budapest (1.d4 Nf6 2.c4 e5!?) I couldn't say.

Not very closely. Although the Budapest looks scarier since White is gaining tempo on the knight, when it moves to g4 Black threats the immediate recapture of the e-pawn; in the Englund Black often loses several moves to recover the pawn, or can play the immediate 2... d6, forgoing all hope of recovering it in favour of rapid piece action.

Of course, if white wanted to decline the Englund Gambit, he could always advance the pawn with d5. However, in the Budapest Gambit, declining the gambit is not a good option. Black will then have an e-pawn that will challenge almost white's entire position.

this is a good move. englund is not a good opening !

Black's choice of 2nd move is interesting. It looks at first sight to be a "beginner's move", yet I see that it has been played at Master level, according to the GK World database. More usual is 2...Nc6, but 2,..d6 is also playable with the idea 2...d6 3.exd6 Bxd6 and quick development for Black.

The bishop on e3 is on its worst possible square, except of course c1. On e3 it is preventing the e-pawn from moving, which in turn seals in the light-squared bishop. Of course, white could always finachetto the bishop with g3 then Bg2, but the dark-squared bishop on e3 is on a weakening square. Why not Bg3?

Good: Black has a fine game now. White's DSB (dark square bishop) is not well placed on e3.

(?) Tricky, but this bishop lacks protection, which means this could have gone nothing for a bishop (9...Qxc5) and a dreadful game.

Another variant is 9... Bxe4 10. Bxd6 cxd6, leaving White a piece down. This was a terribly thought out move.

(?!) Bird in the hand country: I would just have taken the piece. The mate can be stopped, whereupon Black has neither the extra material nor the mate. Still Black's choice argues a flexibility of mind that can be an asset in chess.

(??) Instead 11.Nfd2 would have stopped the mate. Black would no doubt still have had the better of it, but White would still have been in the game. Unfortuantely, intervening with the other knight would have lost a piece (still better than the move played though!): 11.Nbd2 g4! and the f3-knight is "pinned" to the defence of his d2-colleague and may not move.

Well... we all had to learn. Nicely played by Black though.

There were mistakes in this game, but black delivered a good checkmate, and managed to take advantage of white's poor play.