I am writing my Master Thesis. I used code from GitHub for my application and did modifications and extended its functionality to adjust my requirements. I am also citing the code in my own code and text.
My question is that the Github repository doesn't mention any license, which means that the copyright law applies by default. However, i know the author and have their explicit permission to use the code.
What are my options here?. Should i ask the author to upload the license or is it not necessary since i have their permission?.