The free part is about BUILDING the idea, so you don't have to pay anybody to have it done (basically 0 risk and effort). If the idea works, they will get equity, if it doesn't, you didn't lose anything.

It's a mix between a tech cofounder and an investor, and for me, it makes a lot of sense.

Think of free as meaning a "free pass," you get to make a business without failure meaning debt that will follow you around. If the business fails, you walk away with the only thing lost being time