I recently came across a series of articles walking through how to make a scheme interpreter. I was browsing through the code when I realized that it was AGPL.

For the most part, the code itself is the teaching tool. Basically, the code as-is is what I need, however, I did want to understand how it all fits together as well.

I realized though that if I copy and paste a single line of code, my project would become AGPL. Possibly by even more trivial actions?

Anyway, is this a standard practice at all? Am I just being over-paranoid? Also, what benefits are there to this licensing scheme?