From Unofficial BOINC Wiki
The Project Administrator is a member of the Project Staff (or a group of people then referred to as "Administrators") that has the responsibility of the running and maintainence of the project resources. "Resources" include the servers and associated resources needed to keep the servers themselves alive (power, air conditioning, rack space, ordering new parts).
A Project Administrator deals very much with all the technical aspects of a project, and is the person who deals with technical faults and failures related to Project hardware.
In small, start-up projects, the administrator is usually also the Project Director.