Anyone can take either of the backgrounds. A barbarian can take the Initiate of High Sorcery. The listed classes (fight/paladin and sorcerer/wizard) are able to skip the background requirement and just pick the feat as their bonus feat.
lol and this, ladies and gentlemen, is why I don't normally share sneak peeks before a video goes live. my video that premieres in a few hours is about items - magic and otherwise.
You're all going to be mad but, at first glance, I'm not seeing any alignment restrictions for the High Sorcery background options. There is intent though. Each of the orders have descriptions that clearly align to good/neutral/evil, but no mechanical requirement. I plan to work on that video...