Since "geo" means rock and "thermal" means heat, both " Ground Source Energy " and "Geothermal Energy" are terms which have been used for a long time to describe energy which is sourced from the Earth. So it's not surprising there is some confusion.
True geothermal energy is tapped from the Earth's central molten core. In Iceland whole townships are heated using the geothermal heat from subterranean volcanic systems.
The term " Ground Source Energy" is not used to describe heating sourced from the Earth's molten core.
Because the heat from our systems is sourced from the ground (the top 100m of the Earth's crust), we prefer to call this energy source "Ground Source Energy " , even though a 100m bore hole is drilled through mostly rock or "geo"!