I bought better on my MacBook and I want to use it on my iMac at home too. I’m using the same account on both, but on the iMac the App Store only gives me the option to buy. Do I need to buy again?
Probably the developers should reply your question. In any case as from Mojave / iOS12 it is possible to have one app for both OS. Apple has already 3 or 4 own apps, but not heard of anny other as the feature is quite new.
Sorry for such a slow reply, @mariachi. Right now, you can share purchases of Better Blocker for Mac across multiple macs if you use the same Apple ID on those macs. There are instructions on how you can do so in the article below:
Unfortunately Apple does not provide us any other way to share purchases across devices.