I'm glad you enjoy using Souvlakis. Hope you find it useful in learning this quite complicated language.
The project is distributed for free, but some parts of it - like generating learning tips or pages that are missing from Wiktionary - do have a cost to me.
You are free to continue using Souvlakis for free, but if you find it helpful, I would appreciate a small contribution. All donations will go to make sure Souvlakis keeps running.
If you have any questions or suggestions, feel free to reach out: @toomanynights