Stable Diffusion 1.x isn't original work either; it uses OpenAI CLIP. But training your own is pretty doable if you have the budget and enough image/text pairs

Stable Diffusion 1.x isn't original work either; it uses OpenAI CLIP. But training your own is pretty doable if you have the budget and enough image/text pairs. Most people don't have the budget, but at least Midjourney and Google have their own models.