GitHub Copilot is literally GPT adapted for code. The paper on OpenAI Codex, the stuff powering Copilot, makes it very clear in the abstract. https://arxiv.org/abs/2107.03374

Either you call both AI or you call neither AI.

(A previous version of the comment stated that it was tuned from GPT-3. This is incorrect; the simpler GPT was used for faster convergence.)