The key decisions concerning the FreeBSD project, such as the overall direction of the project and who is allowed to add code to the source tree, are made by a core team of some 15 people. There is a much larger team of over 100 committers who are authorized to make changes directly to the FreeBSD source tree.
However, most non-trivial changes are discussed in advance in the mailing lists, and there are no restrictions on who may take part in the discussion.