Does this replace salary?

I imagine so. The specific way income is distributed is up to the employees, though. It could be that everyone gets a certain percentage of the company's surplus income, or there could be fixed pay.

How does one handle a slacker, or someone who has a greater role than others or works part time? Less distribution?

I imagine that slackers would have their pay reduced or something, or maybe the other employees would vote to fire them. Someone with a greater role might receive more pay, but that would be up to the employees to decide. I've read of systems where employees all have equal pay and rotate through different jobs, so that nobody ends up with a greater role than anyone else.