Why does Grover want a searcher's license in Percy Jackson and the Olympians: The Lightning Thief?

Grover, or the "G-Man" is Percy's best friend in this
series of books by Rick Riordan.  He's an unlikely hero, because in his "human" life,
he's bullied and misunderstood, cries easily, is physically inept--actually, crippled
might be a better word (except when the lunchroom is serving a meal he likes, at which
time he ignores the muscular disease which makes mere walking painful, and gets into
line rather quickly).  Grover is kind, perceptive, and a tree hugger of sorts, which is
consistent with his heritage as a satyr.  Getting a "searcher's license" will be
necessary if Grover wishes to search for Pan, the god of wild places, as he tries to
redeem himself after failing to keep Percy safe, as required by his role as a
Keeper.