Contacts and Support
Good way to give feedback is mailing the author (lauri.paatero [at] gmail.com).
Hactar has feedback button. This allows you to send feedback or ask questions related to task ongoing at hactar. Responses will appear as discussion thread.
Support Forum
Hactar has support forum. This is good place for feedback and discussion. Forum requires account creation.
Localizations
If you want to localize Hactar (or improve localization), please see forum posting. Hactar Localization is done at weblate localization. All localizations are created and maintained there.