When wild shaped into an octopus I receive 8 tentacle attacks and a bite attack. Am I allowed to attack eight different enemies (attack/free action grab) and grapple them all? I know I would not be able to maintain the grapple the following round because it is a standard action to maintain a single grapple so I would have to release all my grapppes except for one of them. I'm not sure if I am able to grapple multiple enemies and if I am, what are the penalties I suffer after the first grab is successful? Are there subsequent penalties after each additional enemy I grapple via a free action grab.
Up to 8 creatures, but you take a -20 penalty on each check
Grab has no specific mechanic about maintaining a grapple (other than a +4 bonus), without penalties, that differs from what we got on the grapple rule. So the creature would need a specific entry saying they can do that, like the Abaia:
Endless Coils (Ex): As a full-round action, an abaia can attempt a single combat maneuver check to grapple up to two Large or four Medium or smaller creatures within its reach. Any targets successfully grabbed take constrict damage. The abaia only needs to succeed at one grapple check to maintain a grapple against multiple opponents.
Other than that, you can only grapple and maintain a grapple against multiple creatures if you take a -20 penalty on the CMB check, which can be done once per grappleable-appendage the creature has (for an octopus, 8). From Grab:
The creature has the option to conduct the grapple normally, or simply use the part of its body it used in the grab to hold the opponent. If it chooses to do the latter, it takes a –20 penalty on its CMB check to make and maintain the grapple, but does not gain the grappled condition itself.
You will also notice that a Charnel Collosus (Inner Sea Bestiary) has an ability called Mind Feed that allows itself to be used multiple times against all grappled opponents. But the creature has no means to grapple multiple creatures other than taking the -20 penalty from not gaining the grapple condition granted by Grab.
Also note that this penalty is on that grapple, not on all grapple checks. Which means you can pick as many creatures as you are able to hold with your tentacles.
If you do not release the grapple, you must continue to make a check each round, as a standard action, to maintain the hold. If your target does not break the grapple, you get a +5 circumstance bonus on grapple checks made against the same target in subsequent rounds.
The rule-as-written makes no distinction between the number of creatures on the grapple, if you are somehow able to grapple multiple creatures (grab), maintaining a grapple on all of them should require the same standard action, with the penalties from grab on each check. But according to this other post from James Jacobs, it is better to only grapple a single creature, otherwise the monster might be more difficult than intended by the developers.
One great way to model the tactics of monsters that have really high Intelligence scores (and I reckon a 21 is higher than most GMs out there... certainly higher than mine!), is to be willing to use GM knowledge the monster might not have to make its tactics better, or to backtrack and say "Oh crap, the monster didn't do that, it's too smart to do that... it does THIS instead."
That said, I generally run the rules as they are intended to work, making it so that a monster only grapples one target at a time, because if it doesn't... it's too tough and too badass, generally.
The reason a grizzly bear grapples is that he still gets to do grapple actions. Round one: Grapple. Round two: pin. Round three and on: Eat.
Following on that same line of thought, a few posts later he explains how a giant octopus could maintain the grapple against 8 different grappled enemies:
So if you have a critter that can grab multiple times, such as a giant octopus, would it need a separate standard action to maintain a grapple against each grabbed creature (and therefore only realistically be able to actively grapple one creature at a time), or can it maintain all of its active grapples simultaneously with a single standard action?
Most grabby monsters have the grab ability. That lets them make grapple checks as part of their action if they hit a foe. If an octopus wanted to, it could make the –20 grapple check as part of its free grab action on 8 different foes and maintain them all... but at –20, that might be tricky or tough for the typical giant octopus.