It is allowed by Chess.com's rules.
Opening Explorer

Type "legal" into the Help box at the top left. The first item in the list is a page that includes this ...
No Cheating or Computer Help
You can NEVER use chess programs (Chessmaster, Fritz, etc) to analyze current ongoing games unless specifically permitted (such as a computer tournament, etc). The only type of computer assistance allowed is games databases for opening lines in Turn-based Chess and Vote Chess. You cannot receive ANY outside assistance on Live Chess games.
Also, Erik has just posted this explanation ... http://www.chess.com/forum/view/community/cheating-at-chess-on-chesscom---questions-and-answers

Type "legal" into the Help box at the top left. The first item in the list is a page that includes this ...
No Cheating or Computer Help
You can NEVER use chess programs (Chessmaster, Fritz, etc) to analyze current ongoing games unless specifically permitted (such as a computer tournament, etc). The only type of computer assistance allowed is games databases for opening lines in Turn-based Chess and Vote Chess. You cannot receive ANY outside assistance on Live Chess games.
Thanks.
The opening explorer is a valuable tool and I know it is legal on other sites but wanted to make sure the same applied here.

It is easy to overlook the subtle distinction:
you MAY use Game Explorer on Turn-based Chess.
You MUST NOT use Game Explorer on Live Chess.

It is easy to overlook the subtle distinction:
you MAY use Game Explorer on Turn-based Chess.
You MUST NOT use Game Explorer on Live Chess.
Got it!
Thanks.

It's a very colourful Game Explorer. The board is blue. The green bar is the percentage of games won by wwhhiittee pieces, the red bar is the percentage of games won by black, and the grey bar is the percentage of drawn games.

Yes sometimes its like playing two players in a game, i have put that down to help from friends.
That's an interesting idea. Let the game you're playing diverge from the ones you're looking at in Game Explorer - and try to keep your sanity!
You may have noticed this other discussion http://www.chess.com/forum/view/community/fully-integrated-game-explorer which make the point (among others) that if the various chess.com tools (Game Explorer, Conditional Moves, Analysis Board) were more tightly integrated, we wouldn't have to keep making the same moves in each to keep them in step.
I am curious if it is considered legal to consult the opening explorer on games which are in process. For example, consulting the opening explorer on move 4 to decide the best course of action. I have not seen any topics for or against using the opening explorer.
I am not interested in opinions on this, only the official chess.com stance on subject.
Thanks