As a shop that uses collins, we wrote our own replacement for invisible touch called alchemy linux. The key difference here seems to be that genesis uses scripts embedded into the image, where as alchemy gets the scripts dynamically from its PXE server, and is more of a dumb job runner.
You are correct in that Tumblr did not release Invisible Touch. Genesis is the outcome of lesson learned from IT.
Genesis does not use scripts embedded into the image. In fact this was the original design of IT and much of the reason IT was not released and Genesis was created.
As a shop that uses collins, we wrote our own replacement for invisible touch called alchemy linux. The key difference here seems to be that genesis uses scripts embedded into the image, where as alchemy gets the scripts dynamically from its PXE server, and is more of a dumb job runner.