Comment by spyder

Their difference is mentioned in the paper (and they're saying it's the other way around: Open Sans derived from Noto Sans):

"Open Sans is a general use font derived from Noto Sans. Typographers designed Noto Sans for the small screens on Android devices. "

And they mention Noto Sans having hinting for that:

"Also, five fonts have hinting (i.e., are engineered for reading on screens with low resolutions): Arial, Helvetica, Calibri, Noto Sans, and Times."