The 3e and 3.5e SRD seem to be considered Unlicensed Content now (emphasis mine).It's certainly underhanded...I'm not sure if it's clever. Why didn't they include SRD 3 or SRD 3.5 while they were at it? Paizo doesn't use SRD 5, so they don't get auto-opted into the agreement? Or Wizards thinks they can follow a chain of derivative work back from 5 to 3.5 to 3? The specification of SRD 5.1 is weird to me.
ii. Not Usable D&D Content (“Unlicensed Content”) – This is Dungeons & Dragons content that has been or later will be produced as “official” – that is, released by Wizards of the Coast or any of its predecessors or successors – and is not present in the SRD v. 5.1. Unlicensed Content includes things like the most famous Dungeons & Dragons monsters, characters, magic spells, and things relating to the various settings used in Dungeons & Dragons official content over the years – what the old Open Game License referred to as “Product Identity.” Unlicensed Content is NOT covered by this agreement, and You agree not to use Unlicensed Content unless Your use is specifically authorized by a separate agreement with Us. If You want to include that content in Your work, You must go through the Dungeon Masters Guild or other official channels.