I would say that he can't deploy with them, as scouts deploy after characters, but he can join the unit once the game has begun. Nothing to say that he can't.
he can join the unit as normal. he can not deploy with them as scouts as he does not have teh scout special rule, but if they deploy as normal he can join them from the start of the game
That could be a good choice for a skink chief with blowpipe and venom of the firefly frog. Reroll already poison misses (hitting on a 2+ unmodified). After marching, double tap, and greater than 6 inches would get you hitting on 5+ with him and 6s with the chameleons in the unit.
I have read that Cameleons can deploy with no minimum distance in the woods. Then I tried to show my opponent the rule but could not find it anywhere. Am I crazy, or is it available somewhere.
Page 79 of the big rule book (8th edition). States that they can be deployed anywhere on the battlefield more than 12 inches form the enemy. You cannot charge in the first turn with them though.
In the previous Lizardmen book you could place them as close as you wanted as long as they were out of sight. Alas, now it's just 12" but anywhere you want.