FOSS adware and spyware apps are rare because it’s trivial to fork it and remove the undesirable elements. Users have every incentive to use the ad-free and spyware-free forks, which eventually causes the superior user-friendly forks to overtake the originals. However, proprietary adware and spyware apps cannot be forked in the same way, preventing users from stripping out the ads and tracking. The ability to use, modify, and redistribute “trash software” allows anyone to transform FOSS with undesirable elements into excellent software by removing such elements, whereas proprietary “trash software” remains trashy.
Gumroad made itself more transparent by releasing its source code and becoming a source-available project. That deserves recognition, even though Gumroad is not open source due to its restrictive license. Software is only open source if it does not discriminate against any person or group, even when the discrimination is viewed as positive.