But no, first was the TA (OTA), then there was demo viewer for it, it evolved into Spring engine.
On that engine there were various games - mods of the OTA, such as XTA, BA.
BA was not pretty and had a few balance issues, so bunch of people decided to improve gfx and gameplay and created CA.
CA was developed for many years until most of the OTA content was pretty much gone and replaced from stuff done from scratch. At that moment it was renamed to Zero-K and developed further until it became something that is playable without massive need of laborious tinkering and tweaking from the player.