Is it even partial slavery if he doesn't have voting stock? This article is cute in parts and all, but I really question the legality (and definitely the morality) of this.

He still controls 98+% of shares, which he is choosing not to vote with.

That probably changes things then. I mistakenly assumed that his shares were actually non-voting shares, and that he had no contractual right to vote. If he has voting rights but is just abstaining from using them, then that's quite a bit less crazy.

You weren't mistakingly assuming it, it was mentioned in the intro of the article:

“He kept the remaining 99.1 percent of himself but promised that his shares would be nonvoting.”

There's also no mention of it in the FAQ on kmikeym.com, I'd say it'd be pretty important information to disclose to (potential) investors.

There's a difference between actually non-voting and with voting powers that he has promised investors he will not use.

I'd love to see a source for that. I've browsed quite a few of his websites and read several articles about the project, but I've not come across him saying he has voting shares that he promised not to use.

I doubt there is any case law surrounding voluntary servitude of this nature. I'm not sure one could call this slavery since he voluntarily entered into the relationship with his shareholders. It would be an interesting case, no doubt.

And much of original slavery and indentured servitude was based on the slave being in debt.