The short answer to “What does it take to be a Linux/FOSS contributor, and why be one?” is dedication, and to change the world.
You hear it all the time: Linux and Free/Open Source software depend on contributors. After all, someone has to make all that great software. But what does this really mean? You might think you don’t have any useful skills, or it will be drudgey and no fun, or people will yell at you. The Linux/FOSS universe is very large, and it is quite possible to find yourself in communities that are drudgey and no fun, and people yelling at you. Which is pointless and punitive; why bother? It’s not as though we lack opportunities to enjoy pointless and punitive endeavors.