There are two licensing options for Bookly available:
Regular – lets you use all its features, customize to your liking via admin area or in developer mode, so long as it's used by you or one client, in a single end product which end users are not charged for; the plugin can be installed on one domain only (multiple subdomains allowed).
Extended – allows you to use Bookly in an end product that end users can be charged for.
None of the licenses allows Bookly to be a part of a product that you redistribute.
Note: this applies to the Pro version of Bookly and the add-ons.