You are right, those are similar to Google’s ads, yet they are not personalised.
In fact, as Startpage (formerly ixquick) is a Google proxy, their search results and ads are served by Google. But in contrast to Google, no personal information is collected or transferred to Google in generating or displaying your search results.
Of course, that privacy ends the moment you leave the search site by clicking on a search result link - but that’s true for any one search result, regardless of the search engine you use.
(click for some)
Excerpt from How we keep Startpage.com free without using "personal data"
Our search result pages may include a small number of clearly labeled “sponsored links,” which generate revenue and cover our operational costs. Those links are retrieved from platforms such as Google AdSense. In order to enable the prevention of click fraud, some non-identifying system information is shared, but because we never share personal information or information that could uniquely identify you, the ads we display are not connected to any individual user.
I couldn’t find how DuckDuck covers their operating costs.
With regards to searching, I think DuckDuckGo retrieves its results from Bing, Yahoo and others, so likely produces quite different search results.
But this is beginnig to sound like I am advertising a certain search engine (which it shouldn’t!).
Generally, it’s a good idea to frequent different search engines for both increased privacy and better / more thorough / different search results.
Pick your own - DuckDuckGo and Startpage are by far not the only privacy respecting search engines, and there are lots of other specialised searches out there.