Hmmm . . . this is a really good question, and I think it can be answered by what you think courage is and how that would be played out knowing the type of life Boo lives hiding away in his home.
We know that ever since Boo was arrested for his “wild” antics with some friends and sent to a reform school, he has been hiding away in the Radley house. Whether or not this hermit-like existence is forced upon him by his father and brother, or if it is a choice, is debatable. We will never know because Harper Lee doesn’t ever give us details about what is really going on with Boo and his family. There are so many rumors about Boo, and no one really knows the truth. However, whether Boo is locked away for his own good or whether it is self-imposed, perhaps venturing out of the house could be a sign of courage for Boo.
When Boo leaves presents for Scout and Jem in the knot hole of the tree, he is really telling them something about himself. The carved soap figures, the gum, and especially the spelling medal shows Scout and Jem that he is not the scary phantom that peeps in peoples’ windows and eats squirrels. He is going against the rumors and superstitions that surround him and wants to prove to Scout and Jem that he is normal. This shows Boo’s courage to reach out and dispel the stories about him. In addition, he covers Scout with a blanket during Miss Maudie’s fire, bringing him out of the house and in the sight of others. Although undetected by anyone, this does show Boo’s courage to help Scout and show his compassion.
If Boo has chosen to keep to himself for whatever reason—maybe he hates society and what it represents or he is embarrassed by his past—venturing out of the Radley house shows his courage to want to change and be different from the tall tales and superstitions that surround him. Although small acts, these decisions by Boo could show that courage isn’t necessarily just saving a life but is doing something so extraordinary that no one would believe it.
Because these events are the only time we see Boo Radley in the story, we must make inferences to the meaning of them and how they could show an inkling of courage by our favorite mockingbird, Boo.