What are the requirements for using the Sonic Retro splash screens in a hack/fangame?

For those who don't know what I'm talking about, in some of the Sonic hacks (and I think hacks only) have a additional splash screen which shows the Sonic Retro logo, and depending on the hack, a different animation:


Could anybody just implement their own custom versions for their own hacks and fangames like that, or do any requirements have to be met first (like one has to ask someone specifically for permission).

I myself did something similar for a few Mario fangames I did, in which a splash screen shows the Mario Fan Games Galaxy logo, with it being different depending on the game style.
Super Mario Bros. 3 style:

Mario vs. Donkey Kong style:


I wanted to something simillar for the Sonic project I was planning on doing, and Sonic Retro is the closest MFGG-like site that is about Sonic I think off sooo, yeah.