That's right. Most search engines are funded by advertising, where there is the clear conflict of interest[0], not to mention incentive for spam etc. Alternative models include a subscription fee (which I don't think would work for a small niche search like this) and donations (which may or may not be sustainable). Looking through some of the support forums for the big search engines, I'm pretty sure that enough site owners would pay a fee for support to pay the running costs for a large search engine, although for a smaller search engine like this there needs to be something more than just support, hence the search as a service features.

[0] "Advertising funded search engines will be inherently biased towards the advertisers and away from the needs of consumers", to quote Sergey Brin and Lawrence Page in their "The Anatomy of a Large-Scale Hypertextual Web Search Engine" paper from 1998.