What is the ruling on affiliate marketing for a company that sells servers, hosting, and VPS, and markets CPA offers?

Marketing services are permissible in principle, unless they are for entities that use them for something forbidden, such as usurious banks, or their contracts involve uncertainty (gharar), gambling, or usury. It is permissible to take a commission for marketing for a company that offers permissible services, even if it deals with some forbidden matters, as long as the origin and majority of its dealings are permissible.