Bootlegs are allowed as long as you select "unofficial release" in release type, and explain the item specifics in the listing's details, so people do not think they're legit games. (Bootleg of X game, etc. etc.). Please do not add any ESRB or barcode data to the listings, if they exist, since those ratings are false and usually stolen off legitimate releases.
We already have a large amount of bootleg games in the database but the only identifier we have for them is "unofficial release" so there's no way to browse them on their own - yet. But yes, you can add them as long as you follow the style guide and the rule above.