Ultraviolet is built as layer 2 on top of Bitcoin; it is further evolution of client-side validation with RGB smart contracts, ultra-scalable consensus (Prime), data availability network (Storm) and decentralized scalable computing and machine learning network (Prometheus). It is created by Pandora Prime SA.
Ultraviolet consists of a family of protocols and products. Its development is spread across a number of Github organization. Here are the navigational links to all of them: