To clarify this: The source is neither Google nor Landsat but a completed and stand-alone scientific work published here https://www.seanoe.org/data/00765/87740/ , which in itself among many other sources used also Google and Landsat. The correct attribution is made in the attribution tag. I will suggest to clarify this in the source, i.e. name the primary source https://www.seanoe.org/data/00765/87740/, and only give indication that this completed work has been performed with diferent satellite imagery, in some cases including indirectly also Google and Landsat. 
I hope this makes it clear, and clarification of CC BY 4.0 permission for the original and primiary source for OSM is already requested.
Thank you very much for your reviews and indication of clarifications to be done for using the published data in OSM. I hope to get feedback of the authors soon and will then open a dedicated wiki page for further description and discussion. Your further input will be very welcome. Greetings, Josail