licensing - WP Developing

Can one purchase an extended license to the plugin so that one can include it in one’s themes?

Not currently.

Can the license be used across multiple domains? What about on subdomains?

Sabai: It can only be used on a single domain.

Me: The answer from Sabai Apps is unclear about subdomains, however, I have used it on subdomains for testing purposes and it seems to work fine.