NOTE: EMF Query, along with the rest of EMF Services, has moved to GitHub. The new official location of the source code is at https://github.com/eclipse/emf-query.
The EMF Query component which lives here is officially no longer supported or maintained as of May 2020. Starting from version 1.13, EMF Services will no longer ship this component.
In practice, the last non-trivial source code change dates back to December 2009, so this is really just making official the long-existing situation.
If someone is interested in reviving this component and maintaining it, please contact the project lead or committers of the EMF Services project, of which EMF Query is/was a sub-component: https://projects.eclipse.org/projects/modeling.emfservices/who.