GFO is the ontology of GOL, the General Ontological Language from the same research group in Leipzig. The purpose of the ongoing effort is to create a formal framework that can be used to create domain-specific ontologies. The foundation of this will be a set of top-level ontologies, that can be used in this framework.
Since this work is supposed to be more theoretical in nature, we will focus on the set of top-level ontologies used in GOL, the General Formal Ontology. GFO defines a set of categories, that remain unaltered in every ontology of GFO. However, one can choose between different axiom-systems.