One of the key things about Bahmni that differentiates it is that most of the EMR screens / fields in Bahmni are configurable via JSON / Administrator UI. You don't need to fork / code / branch to make these changes. In some places you can also change the order in which screens get rendered via configuration. So, your Bahmni config stays separate from the "product", which allows you to upgrade and get new features without having to manage your own version of Bahmni. All you need to manage is the metadata.
The plan is to integrate with OCL in the future, so that even metadata management can happen via a github like terminology system: https://talk.openmrs.org/t/introducing-open-concept-lab-for-...