Hi there, of course!
If premium (paid) code is executed at runtime, this is disallowed. This would include the Havok physics engine included in Unity Pro. Using the premium editor features is permitted. Premium assets are also disallowed, but premium tools that you use to create assets such as Photoshop, 3ds Max or Maya, and FL Studio are permitted. Using premium assets as a foundation to modify within these tools is disallowed, such as premium models, stock images, or music loops.