Actually as I understand it, the official ninth game in the series through Activison is being produced by Telltale sometime in the future. It won't be free.
TSL is a fan game, made by the fans, for the fans (although not every fan agrees with POS take on the series). So it is a work of fan fiction.
While it was initially called King's Quest IX on early versions of the website, that was dropped later on, as part of the agreement for the fan license.
We can thank fangames like TSL, IA's KQ3, and AGDI's trilogy, for pushing Activision to bring the official series back to life!