The history, as I understand it, is this:
1. 7bit's Round 4 gets a Space Cadet colorway added (called "SPH"), the only spherical set in a GB otherwise comprised of DCS keycaps. 7bit announces his intention to eventually create the special Space Cadet legends for a future GB.
2. xblackdog is inspired by this to create Symbiosis, which has the greek characters as secondary alpha legends, but suffers from being uniform R3 and somewhat "inaccurate" in other minor ways.
3. 7bit completes the Space Cadet legends and makes them the centerpiece of the Round 6 (formerly known as Round 5a) group buy.
The Round 6 group buy also included a re-run of the Round 5 Honeywell colors, but due to funding complications, only the Space Cadet (blue/gray) and purple/cream keycaps from Round 6 have been produced so far. They are shipping to customers as we speak.
As for being an "on-going thing," that is only true to the extent to which there are blue/gray leftovers from Round 6 still available for people to snatch up.