I'm going to leech off of my friends science project
Why would you leech off of his project?
I think it wouldn't hurt considering he has been so helpful in the past.
You shouldn't take advantage of your friend's good nature like that. On the outside he may be smiling, but on the inside he could be fuming, knowing that you are taking advantage of him. This may end the friendship suddenly one day when he finally has enough.
I'm not the bad person, it is something I intend to repay in the future.
Are you sure? How would you do that I wonder. I still think that you should just not leech period in order to not make waves.