I disagree, he is extremely courageous. The fact that he does it not out of some sense of innate heroism and adventuring desire makes him even greater. He's not there due to anything else other than is sense of right and wrong.

There are several heroes in LOTR:

- The more "heroic" archetype of Aragorn

- The flawed character of Boromir that atones himself for his sins with one last heroic stand

- The unwilling but ultimately acceptance of Frodo

- The more laidback silly courage of Merry and Piping

- The devoted courage of Sam

- Even Galdalf, when he faces that fiery beast (I don't remember the name right now) and Sauruman.

- And there are many side characters that also fit the role (like the Rohirim)

It is truly a tale full or heroes and several acts of great courage. Many of them might not have gotten into it willingly, but they surely took on the role seriously and honorably.