Blues Guitar Lesson - Sliding 9th Technique

doood, you are an inspirationnnnn ;D!!

that looks like a major 7th chord to me....no?

A dominant G9 chord without the root is a Bmin7b5 or half diminshed chord. I hate that name though.

YEah! Nice job with the video

Mike rocks! Thanks for posting sir. Gives this beginner better ideas and easier to understand lessons than anyone else I've had try and teach me.

Gracious mon ami!!!_;)

Good stuff, but would you please PLAY the licks first...then talk and show...easier for us to get the picture

its not a diminished chord... its a G9 chord with the minor seventh

That grip would be a diminished chord if it were being played on the top four strings, but on these four strings it's a rootless 9 chord: low to high: b (3) f (b7) a (9) and d (5).
Also, this is the I (one) chord, not the 'root' chord. The term root refers to the low 1 note of the chord (g in this case, which happens to be omitted).

Bare in mind he said that he would be playing along with another track so that would be covering the G.

Yes it could be seen as a diminished chord but in this context he's using it as a G7 chord:

G A BC D E F

G (root) - B (major 3rd) - F (flat7)

Notice when he slides the chord he removes his index finger (what would be the B in this chord shape, the bass note) the three fingered shape he's left with is a major 7 triad.