Usually, going "Gold" means you have reached a certain number of sold units (half a million?).
In AmigaLand, it means announcing that your product is nearly released.:roll:
Going gold is a pretty standard phrase in the software industry, moreso with games, though. Blizzard (used to) use it all the time for their impending releases.
I think it's only the music industry that uses it to chart number of sales.