PathOfPriceCheck identifies itself to GGG's servers with this User-Agent:
PathOfPriceCheck/<version> (+https://github.com/JIRPOS/PathOfPriceCheck-Data)
GGG's public-API policy asks that unregistered clients offer a route to reach the maintainer, which is why that URL points here rather than at the (private) app repository.
To reach the maintainer, open an issue. Issues are read and this is the fastest route for anything about the tool's API usage.
For takedown requests concerning the generated data, see DATA-LICENSE.md; an issue works for those too, and will be actioned.