It’s completely open-source, so it’s easy to fork and self-host if you want to avoid lock-in. I originally built it for myself and don’t have plans to monetize it. Even if I do in the future, the current version will always stay free and without sign-up. Any monetization would come as a separate pro version with extra features, not by removing what’s already available =)

Github: https://github.com/VladSez/easy-invoice-pdf