While I can not prove it in THEIR eyes, I have purchased all of the books (aside of the adventure books, as I see those as DM terrority and I am not a DM). I will not use D&D Beyond for a few reasons. 1) Where I play I do not have access to the internet. They have internet, but it is limited to store employee use only (they do not have the bandwith for everybody). 2) To use this produce I would have to buy digital copies of books that I already own. I am on a fixed income and can not spend hundreds on duplicate materials. 3) I have looked at D&D Beyond, and aside of an additional monthly fee and the aforementioned reasons, I feel the interface is awful. Truely awful.
I get why WOTC is doing what they are doing...because the character generator goes far beyond what is allowed in the SRD, but given that no money is exchanged I would think they have tenuous legal grounds at best. Note that they are not telling FA to take it down (as far as I can tell) but rather they are telling his host to take it down. Sometimes you don't sue for the money, sometimes it is to make it more trouble than it's worth to fight. Goliath vs David: David doesn't always win.