"I do not lend notes."
Translation:Nie pożyczam notatek.
Well, imagine it's "money" instead of "notes" - is it clearer now? A fellow students wants to borrow your notes, but you don't want to do it, maybe simply because you worry that he will not give them back to you.
Or that they want to pass the exam basing on your notes when they weren't even present on the lectures while you were present on all/most of them, that would be them passing on your cost. There is even a saying in Polish: "dobry zwyczaj - nie pożyczaj" (literally "a good custom - don't lend"). Concerning money/stuff/etc.