I can't speak to balance in it's latest form, but it is not AL legal. It's a home-brew class by Matthew Mercer, DM of Critical Role. As part of the new campaign being run, they have an ongoing sponsorship from D&D Beyond, and D&D Beyond have put up his class on the site. It's not an officially released class by WotC.
While it's not official, it's probably the most play tested home-brew class to exist, due to the size of the Critical Role following. I had a player play one in a previous campaign around level 6 and it was fine. Nothing overpowered, in fact he was probably the weakest character. It has some interesting thematic and mechanical things going on though, with sacrificing HP to strengthen their attacks. I've heard that the Order of the Lycan subclass might be too strong though due to some resistances they gain.
