a) What do you call this at the bottom of the page https://www.hudsonrivertrading.com/liquidity/

b) If you don't have customers, why have a company?

I think you're misunderstanding what that page is: it's not an advertisement to invest with the company, it's an advertisement to trade via/with the company in the same way you might otherwise go manually trade from a Bloomberg terminal (or any other method).

There is no way to invest in the company, and the only way of becoming a "customer" is to engage in trading.

I don’t really understand question b), how else would you organize a venture involving more than a couple people?