There are a lot of people with very strong incentives to keep Fluxus dead. Dead Fluxus serves the financial interests of a group of collectors and museums. Art Historians like their movements to have beginning dates and end dates, it makes those litle time-bar graphs so much more appealing. And a small group of people who were close personally to George Maciunas worry endlessly that his legacy will somehow be diluted if Fluxus didn't die with him.
When George Maciunas coined the name "Fluxus" and attached it to the work that he and a circle of likeminded people were making, something akin to Fluxus was already happening. This work was an amalgamation of ideas from Dada, Zen, John Cage, Ray Johnson, Black Mountain College. Many artists, writers, composers, and other creators were creating work that was very Fluxus even before George Maciunas attached a name to this work, and built a circle of like-minded creators around himself. I am confident that if there was no George Maciuans there would still have been a Fluxus - it would have been called something else perhaps, but the Fluxus meme already existed.
George Maciunas did not own Fluxus. He may have thought that he did, and it seems that there are 2 or three people who believe that he did, but there were many, many artists working contemporaneously with Maciunas who were also Fluxus, and subsequently there have been dozens, if not hundreds of artists (and anti-artists, poets, creators, etc.) who were, and still are Fluxus.
Fluxus happened. Fluxus is still happening. It is happening whether that is acknowledged by the School of Old Dead Fluxus or not. Of course, I would be thrilled if Living Fluxus was acknowledged by the remaining members of the Original Fluxus circle... but, whether Living Fluxus is acknowledged or not, there is the very real phenomenon of Contemporary Fluxus. That Fluxus is alive and well is not plausably deniable. The Fluxus meme is still alive, and creators around the world are working in the Fluxus milieu. The only way you can look up at the sun and say that it's night time is if your eyes are closed, or you are blind.