Does anyone pay for placement?
No. Download links go only to the official windirstat/windirstat GitHub release, Microsoft's winget catalogue and the Microsoft Store listing named in the WinDirStat README, because those are the official sources, not because of any arrangement. The comparisons with WizTree, TreeSize and SpaceSniffer are written from each vendor's own product pages, and none of those vendors has seen or paid for them.
What if advertising is added later?
If display advertising is ever switched on, it will appear only in clearly labelled slots, this page will name the ad network first, and the privacy policy will explain its cookies and how to opt out. Advertising will not change which sources, commands or products the guides recommend. Sponsored articles and paid links inside guides are not accepted.
Who is behind the site?
The About page describes the publisher and the editorial policy explains how facts are checked.