This is the modern defence

Not yet. It depends on the next few moves. The current position is very flexible. While the Queen's Pawn openings have a reputation as being more positional than the kingside ones, don't fall into the trap of assuming that your opponent is only comfortable playing positionally. Some of these Queen's Pawn openings can get very tactical, especially when Black played Indian-type defences. If White plays 1.d4, he has to be prepared for those as well as the closed openings.

Normally - for a given value of 'normal' - Black would have played a knight to f6 by now. Black's present handling of the opening is a bit more provocative, waiting to see whether the g8-knight might be better placed on, say, h6. GM Duncan Suttles used to play something like this.

Whatever his intention, he has certainly staked out the center for himself.

OK, but I would have been tempted to play 6...Nh6 or 6...Ne7, preparing to castle, but also leaving the f-pawn free to advance to f5 - the thematic break.

And that's called a "Dutch" opening, right ?

by "thematic break" do you mean that it is no longer in the book?

The Dutch does feature an early ...f5, usually on move 1. A later ...f5 is a common feature of the Modern, King's Indian and Queen's Indian defences. Now that Black has played ...Ngf6, we've definitely transposed into a well-tried line of the King's Indian. "Thematic break" does not necessarily mean that the move at this point is not in the book, just that it's one of those moves one expects sooner or later in this style of opening. Once a knight has gone to f6, Black has to spend longer preparing it, hence Ion's preference for moving the knight elsewhere.

Thematic: White is planning, by c4-c5 to hit Black's base at d6. The scheme is to leave the d6 point weak and vulnerable to attack.

I think this is the "Bayonet Attack", a tactical means of imposing White's strategic will on the game.

This move also inhibits c4-c5.

Not a move I would have thought of at once. Black's usual plan hereabouts is ...0-0, ...Nh5 or ...Ne8 (whichever seems safest or more convenient), ...f5, and probably ...f4, beginning a pawn storm on the K-side.

It's quite often played as an immediate response to White's b4. There's a lot to be said for stalling White's Queenside assault before starting Black's Kingside assault. If the attempt to stall White fails, though, Black generally has a lost game.

I'm inclined to disagree with that assessment. This advance looks tidy, and stymies Black's counteraction on the Q-side. But that is of little real concern for Black. The problem for White is, how is he to conjure up any kind of play on this side of the board, now? What can he do on the K-side? That is where Black wants to attack! Better, I think, was 9.bxa5.

I agree with Ion. White has just allowed his assault to be stalled, leaving Black a free hand to develop his Kingside counter-attack.

This is a really bad move by white. With white, I play this kind of scheme against the King's Indian, and its all about overwhelming black on the queenside before he has any time to set up an attack on the kingside. Now that the queenside pawns are all blocked, black will seize the initiative in no time. 9. bxa5 was definitely better.

... a further downside of White's 9th move.

If 10.Bd3 Nfxe4 11.Bxe4 Nxe4 12.Nxe4 f5 (hoping for, say, 13.Nc3 e4) 13.Bg5 Qd7 14.Nf6+ Bxf6 15.Bxf6 0-0 (yes, the move is legal) 16.Bg5 and White has piece for 2 pawns. Probably White chose the Q move as he preferred to keep his B move actively placed on e2, or else he feared ...Nxd3. I doubt that Black would want to exchange his muscular N on c5 for the 90-pound weakling bishop on d3.

Ion, that bishop must be more than triple weighted! Indeed, any 10. ... N(f/c)xe4 after 10. Bd3 does not seem like a good idea. But 7. .. b6 and 8. .. a5 were well played.

Extraordinary! Creative thinking, and shows some flexibility of thought. But castling would have been fine. Black has better prospects of attack on the K-side than White has!

Nice! I'm impressed!

Yes - interesting. Given the clogged up pawns in the centre, the King should be safe in the centre, so the main objective of castling is achieved. It will be interesting to see how Black prosecutes his attack with the rooks, queen and QB all still undeveloped.

I like that move too, may be I would hide it one more move by playing Nh5 first. Now white might decide not to castle short either. Black looks already better here. About the development of the rooks: They should go to open files, the one on h8 is already perfectly positioned.