Short answers, pulled from the story.
Star Wars Galaxies shut down on the 15th of December 2011, at 9:01 PM Pacific time due to the expiration of the contract between Sony Online Entertainment and LucasArts. The shutdown was announced jointly by both companies on the 24th of June 2011.
The New Game Enhancement (NGE) was a major overhaul implemented in November 2005 that replaced the original 34-profession skill system with nine streamlined professions and changed ground combat to a real-time, first-person-shooter style. The NGE drew widespread criticism and coincided with a surge in subscription cancellations; Sony Online Entertainment president John Smedley later called the decisions "stupid" in a July 2012 Reddit interview.
The base game launched with 10 planets: Tatooine, Naboo, Corellia, Talus, Rori, Dantooine, Lok, Yavin 4, the Forest Moon of Endor, and Dathomir. Paid expansions added Kashyyyk and Mustafar, and Hoth was added in November 2008.
Star Wars Galaxies was developed by Sony Online Entertainment and published by LucasArts. The project began in 2000 as a partnership between LucasArts Entertainment, Verant Interactive Inc. (creators of EverQuest), and Sony Online Entertainment.
Yes, through emulator projects. SWGEmu, founded in 2004, aims to recreate the pre-Combat Upgrade version of the game at patch 14.1 and is open source under the GNU Affero General Public License. A separate project, Project SWG, works to emulate the NGE version; its server Holocore remains under development.
By August 2006, the base game Star Wars Galaxies: An Empire Divided had sold 370,000 copies in the United States, generating $16.1 million, making it the 43rd best-selling computer game in the country between January 2000 and August 2006. Combined sales of all Star Wars Galaxies-related games in the United States reached 720,000 units over the same period.