Homebrew is not suited well for DMG package distribution (well, at least I don't know examples of such software).
But you can install Marta just as any another macOS GUI software.
https://github.com/caskroom/homebrew-cask
EDIT: details on how to add your own Cask for an app:
https://github.com/caskroom/homebrew-cask/blob/master/doc/de...