Diaspora is written in Ruby on Rails and therefore knows different running modes. These have nothing to do with running from the master or the develop tree. Nonetheless we recommend the development mode for development setups and production mode for production setups. The difference is, apart from a slightly different default configuration, speed. The development mode reloads the code on each request, so it speeds up your development. The production mode doesn't do that, so pages load significantly faster. That's the only major difference you need to care about. To emphasize it one more time: Running a production setup in development mode gains you nothing.
Lastly you can choose between running on MySQL/MariaDB or PostgreSQL, in our experience PostgreSQL achieves a better performance.