[1]Pete Hunt, who at the time was an engineering manager at Instagram as well as one of the more prominent members of Facebook's React core team, is willing to shed some light on React's beginnings.
Also helping to tell the story is Paul O'Shannessy, one of the first engineers at Facebook to be dedicated to React full time.
People[1] who were there when it started seem to be OK with calling it framework:
http://queue.acm.org/detail.cfm?id=2994373
[1]Pete Hunt, who at the time was an engineering manager at Instagram as well as one of the more prominent members of Facebook's React core team, is willing to shed some light on React's beginnings.
Also helping to tell the story is Paul O'Shannessy, one of the first engineers at Facebook to be dedicated to React full time.