It may count as being commercial for the Youtube part (advertisements) but it is definitly a derivative work. As Carsie Blanton choosed a "No Derivatives" option you have to ask her for the use of her songs in your short films (http://www.carsieblanton.com/)
I'm doing short films for a film school project, non profit just for class and it will be uploaded to the school site and you tube though, does this count as being commercial or not?