@itsginnydi If we use the technical definition (as related to computer software) then "Backward compatible (also known as downward compatible or backward compatibility) refers to a system that can successfully use data from earlier versions of the system. (my paraphrase) then yes.
@GhostfireG@luboffin I loved that they recognized that releasing the SRD under Creative Commons may be WotC's way of cutting ties with 5e and that OneDND will be a new version with no compatibility to 5e.