Sam found it slightly amusing that jack wouldn't invite Jonas to join the team because he was an alien, especially since Teal'c looks more alien than Jonas does.
But the truth is, Jack doesn't think of Teal'c as an alien anymore, he never really did, from the first moment he met Teal'c he knew they would be brothers, something in jack isn't very smart, but he knows people, something in his gut tells him these things, these bright sparks of intuition he has.
Teal'c is black, jack is white, Teal'c has a snake in his gut and jack has intestines and cake, but still, jack thinks Teal'c is more like him, more human than Jonas will ever be.
He's not sure why but he thinks maybe in ten years Teal'c will still be here on earth and Jonas wont.
Earth is Teal'c's home, he was born Jaffa, but jack thinks he'll probably die Tau'ri.
Teal'c hasn't been an alien for a very long time, he's always been a little different, weird, has bad humour, the snake in his gut is defiantly alien, but jack thinks Teal'c has never been alien.
Teal'c's always been his brother.