A project management committee is a group of people assigned responsiblity by the board of the foundation for the governace and oversight of a project. This form, like any interface, has a bit of tension from both sides.
The foundation strives to leave oversight in the hands of the people working on the project. We are not attempting to mimic the hierarchitcal management of a firm. We do not have the single minded goal (profit) of a firm. Instead we have the goals of a nonprofit - to do good works for public benefit; i.e. to create a PublicGood.
The foundation, and in turn the board, have assorted legal responsiblities. For example there are plenty of legal responsiblities regarding intelectual property that the board and the ProjectMangementCommitteeChairman must assure are taken care of. The board ...
This tension creates some odd push and pull. For example the board is the only legal entity that can specify who is a member of a project management committee, but meanwhile the board has delegated that responsiblity to the PMC chairs; who, presumably delegate it to the committee.
Another example of this tension is the board's struggle to assure that the committee's are run in a manner that assures they achieve the right degree of oversight; for example should the board be blind to what a committee is doing then they aren't doing their job. On the other hand if the board is reluctant to intrude into the operation of a committee since we believe that's an extremely ineffective way to do open source.
From time to time, but rarely, the board intrudes into the operation of a committee. Presumably because something is broken. What's broken might be something legal (like an intelectual property issue), something related to their oversight responsiblity (like lack of reporting etc.), something related to the mission of the foundation (like the project looks highly likely to blow up or evaporate and hence not create a PublicGood).