What is the difference between free, Pro and subscriptions???

[TjShredder]

This certainly is missing in the FAQs. Before spending money I would love to know... Searching the net, unfortunately doesn't tell me anything about it... I am a happy user of Kybook 1, but without knowing the differences I hesitate to port all my books to Kybook 3... Btw. I am not interested in subscriptions at all, and don't need any cloud services...