FreeBSD's documentation falls into four basic categories;
The Project does not really concern itself with these, since they are a part of the base system. The exception to this is the Japanese team, who are translating them. There is no reason other volunteers could not step in to translate the manual pages to other languages as well.
That is not to say that the manual pages are unimportant, far from it. It is just that they are intimately tied to specific systems of FreeBSD, and most of the time the best person to write the manual page is the person that wrote that part of FreeBSD.
This is maintained by the project. The aim is to address (in short question and answer format) questions that are asked or should be asked on the various mailing lists and newsgroups devoted to FreeBSD. The format does not permit long winded and comprehensive answers.
This is maintained by the project. Topics that need a more in depth discussion are addressed in the Handbook.
Some of these tutorials are maintained by Project committers, others are not. The maintenance of these documents is up to the individual authors, although, to the best of my knowledge, they have all kept them up to date, solicit comments from the readership and so on.
Some of the tutorials are stored on the FreeBSD web site. For these tutorials the authors submit their changes to one of the committers, and the committer makes the change. Other tutorials are stored on the author's private webspace, and the author can make changes as and when they wish. Sometimes this is a deliberate choice on the part of the author, and sometimes it is a historical accident.