The GHTV service that supported Guitar Hero Live is going to be taken offline on December 1, Activision has confirmed. The process actually started on June 1, when the mobile version of the game was removed from the iOS Store and in-game purchases were turned off for one and all (although you'll be able to use any credits you have before the service shuts down in December and carry on playing the offline portion of the game as normal).
GHTV was designed as a service for players who wanted to play along with a continuous stream of tracks, an interactive MTV if you like. However, despite its ambitious premise, its closure is a sign of the times for the series. A decade ago these types of musical games were on top of the world before their popularity eventually diminished. More recently the genre enjoyed a mini-revival via Guitar Hero Live and Rock Band 4, but that return to prominence seems to have tailed off as well.