yes and no. you can't sign your app with a certificate so if you want to have a frictionless install you have to pay. (the friction is having to explain that you have to press ctrl while clicking and then click open and then click trust this app) command line utilities don't have this friction and brew mainly installs command line utilities (though there are app binaries distributed through a separate brew thing... keg or cask or cellar or something like that)

traditionally you would need to pay the 99 bucks to install a binary on your ipad or iphone or iwatch. those need to have the certificate signed by apple to run on the phone for general security reasons so some website couldn't sideload an app. now you can do all of that without paying the 99 bucks... but if you wanted to sell it on the app store or distribute it for external testing you still need to pay.

> general security reasons

Cash cow reasons*. The system is designed to be secure even against signed apps.

Yes, all of it is open for development. The only thing about mac is that, if you want to distribute apps via the web, you'll need to instruct the user to bypass the code signing requirement by right-clicking on the app or DMG and clicking open from there. Getting a Developer ID code signing certificate is only available with a paid developer account.

> Never used a mac, but I assume that is only for installing from the store, correct?

Incorrect, and why would you try to answer someone's question when you admittedly have no knowledge of the situation?