A HUD is a HUD
sure but the HUD from the F-35 is very specifically designed to work in an F-35. It's very similar, and comes from the same family, as the software running on other planes. But it's not identical.
And yes, performance limits would be hard coded into the software because the HUD needs to alert the pilot when they are getting close.
Edit: and that's ignoring the fact that a lot of this stuff comes from private companies so you'll run into things like IP/patent laws