Certain decision had to be made. Particularly, decision about the technology use, convensions, standards, etc. The below linked documents describe the choices made or options being considered.
As you will see, most of these decisions are non-negotiable. This isn't to be difficult, or to cut any developer out of the decision making process (lots of things left to do and decisions to be made). The reason for doing this, is that a lot of the non-negotiable decision involve "holy wars" eg bracing style. So, by doing this, these "holy wars" will not be an issue.