A shown in the examples:graphexplorer/GraphObjectRef it is possible to clone the data graph of a GraphObject and add it to the project Graph.

// create the reference to the imported GraphObject
GraphObjectRef gufi = new GraphObjectRef("gufi1.dtd");

protected void init ()
[
    //initialize the project with a clone of the graph object
    Axiom ==> gufi.cloneGraph();
]

This adds a copy of the content (all Nodes) of the GraphObject to the project graph, the content of the project graph is afterwards completely independent from the GraphObject.