Checking my copy of the book, it describes grapple as being an improved version of the grab action, available if you've taken certain feats.
Trip and Throw are easy enough. The grapple ends when you execute those feats.
For Pin however, since the feat benefit states the target is flat-footed until the start of your next turn, which would be indicative of the target not being able to easily break free since they'd still be penalized. Of course, it could be viewed as the target had to spend such effort to escape the Pin that they are still recovering for a few seconds, hence flat-footed until the start of your next turn.
I am inclined to agree with Baby Samurai that it just takes a standard action to break out of a grapple, as that's the simplest solution and most of the questions that have come up in regards to Saga Edition have pretty simple solutions.