[moeffju]

The economics don't matter, everything that is regularly updated or offers a service needs an Impressum. The exception for "purely personal or familial" use clearly doesn't apply here because a service is being provided actively.

[echoangle]

Here’s the law: https://dejure.org/gesetze/TMG/5.html

It mandates a Impressum for „ geschäftsmäßige, in der Regel gegen Entgelt angebotene Telemedien“. If it’s not geschäftsmäßig (Business-Like?), you don’t need an Impressum. If you do it for free without any intention to make money now or later, it’s not geschäftsmäßig.

If I have a blog that I update regularly but don’t have any ads from or take donations for, I don’t need an Impressum.