From GEM website
For PhD Students:
"During the first academic year of being awarded the GEM Fellowship, the GEM Consortium remits a stipend and a cost of instruction grant to the institution where the fellow is enrolled. Thereafter, up to the fifth year of the doctoral program, continued financial support of the GEM Fellow is borne by the GEM University through alternative sources of funding such as institutional awards, assistantships or other external fellowships. " - http://www.gemfellowship.org/students/gem-fellowship-program/
Basically GEM pays for a year and the university covers the rest is how I'm reading this.