What is the ruling on dealing with an e-marketing company that grants in-kind gifts (electronic devices) to those who register people with it for free, in exchange for points calculated for each registration, knowing that neither the registrants nor the marketer pay any money?

Brokerage is permissible and is a type of ju'alah (commission/reward-based contract). So, if the company gives gifts as payment to someone who markets or promotes for it, this is permissible, provided that what is being promoted is also permissible. It is not permissible to set specific points below which payment is not deserved; rather, each person should be given according to their effort and production. The worker deserves the ju'alah payment in proportion to what they have accomplished of the work. Thus, whoever brings five customers deserves half of what someone who brings ten customers deserves.