This is the fulfillment page for MUI X Premium, a plan listed on the pricing page. For context, MUI X provides React components that extend MUI Core (e.g. Material UI). Some of the features are MIT, and some are not. The software that is not MIT but under the Premium plan can be purchased here.
⚠️ MUI X Premium doesn't include any design assets, you can find Figma and more under the "Design" section.
Here are a couple of resources that you might be looking for: