There doesn't seem to be a universal answer. There may be some desire to distance themselves from the extremes of their early years, or to keep sounding fresh and relevant as the culture around them changes.
Great Commission Churches (GCC) is the current name of the umbrella organization that provides guidance, training, and accountability to the local churches. However, local churches are considered to be independent. You can read more about this at GCC's website,
http://gccweb.org/about/.
GCC has a subsidiary called Reliant, formerly known as Great Commission Ministries (or maybe Great Commission Missions, not sure) or GCM, which oversees church planting and campus ministries. Because the names GCC and GCM were so similar, many people on this board just refer to the whole conglomerate as GC or GCx. You can read a bit of Reliant's organizational history on their website,
https://reliant.org/about/our-full-story.
This isn't a complete answer to your question, but we don't actually know what the leaders are trying to accomplish with so many name changes. We just know that it's an ongoing pattern of behavior within the movement.
If I got any details wrong, I welcome corrections.
