I haven't heard about someone ever getting a letter for seeding books, but maybe I'm lucky. In any case, I'll add a notice to the README, thank you for the suggestion.
It would likely happen in Germany, unless you have a VPN. This has been a problem for years when torrenting films. Chasing people with fines has been a lucrative, automated business for years.
A decade ago, it happened regularly, but not sure if they are still doing this now. But the laws haven't changed much since then.
Well, there's a very famous story of one of the cofounders of reddit facing a million dollar fine and 35 years in prison for just downloading, not seeding, scientific articles. Not entirely the same, but quite related as his motivations were similar to those of Anna's Archive.
https://en.wikipedia.org/wiki/United_States_v._Swartz