IMO, if a splat is mentioned in the Errata and included by default in Anathema, it can't be homebrew. The
Ink Monkeys PDF was fan-made, but the content is official. Relevant are the 20 pages of Solar stuff (lots of which are Mirrored) and 12 pages of Abyssal stuff. In your position, I would at the very least open up that, the Errata, Lords/First Age, and Glories UCS.
(Since there's so much Exalted homebrew that's actually really good - though I don't actually know of any for Abyssals - and every GM's stance is different, it ultimately comes down to "Hey, [GM], can we use this? [link]" "[Yes/No]")