If you need a specific production-ready version rather than the latest "in-development" code, use the Releases section:
The standard way to get a ZIP of the Ghost CMS or a specific Ghost theme is through the repository’s main page: to the Ghost repository on GitHub .
You can bypass the UI by appending a specific path to the repository URL in your browser: Download repository Ghost zip
under the Assets section to start the download. 3. Direct URL Method
located near the top right of the file list. Select "Download ZIP" from the dropdown menu. If you need a specific production-ready version rather
on the right side of the Ghost repository.
once the download is complete to access the source code. 2. Download from the Releases Page Direct URL Method located near the top right
How to download source in ZIP format from GitHub? [duplicate]