According to the website:
it is evident from various sources that a remarkably diverse range of immigrants entered England during the later Middle Ages, from other parts of the British Isles, from the near-continent, and from other, more distant locations. It is also clear that these people were drawn from a far broader variety of social and economic backgrounds than just the upper echelons on which modern research has concentrated.
The project is managed by the University of York, in collaboration with The National Archives and the Humanities Research Institute, University of Sheffield, and is funded by the Arts and Humanities Research Council. Personnel working on the project are listed here.