Whether you actively try to recruit one of your registered users to add our API or not, there are plenty of incentives and opportunities for them to do so on their own. It really is a situation where they "have nothing to lose" so their is never any "sales pressure".
If they have a website, they are potentially "recruited" when they register at your API to receive free or paid advertising from our network. If and/or when they decide to install the API too they will be able to earn you commissions on their sales.
We also have available free personal blogs at over a dozen WordPress MultiUser websites where users can essentially get a free website if they don't have one (or if their website isn't compatible with our API).
The links for them to register for all of these opportunities are included in a menu along the top of your own API. They can review the programs, pick the one they want, register and get started. When they do (from your API) they are registered as being your recruit.
It's important to remember that even if someone merely signs up for the free advertising they could eventually be recruited. Everyone that registers for advertising at your API is registered to your account whether they become an active recruit immediately or do so later.