As conceived of in most of the literature, "gold open access" refers to the means of dissemination (done by the publisher), not any one specific business model. Gold open access does not intrinsically mean, however, that the author pays and, indeed, this was not integral to the term as it was coined by Stevan Harnad. At the time of writing in mid 2014, the majority of gold venues listed in the Directory of Open Access Journals do not operate on the basis of article processing charges and instead fund their operations through other means.
For more on this, see:
Suber, Peter. Open Access. Cambridge, MA: MIT Press, 2012.
Eve, Martin Paul. Open Access and the Humanities: Contexts, Controversies and the Future. Cambridge: Cambridge University Press, 2014.
(Both books available freely online; gold open access.)
http://blogs.egu.eu/network/palaeoblog/files/2015/02/OpenGlossary1.pdf
http://legacy.earlham.edu/~peters/fos/overview.htm