At the bottom of the page (Launch: Integrate your marketing tools with open APIs | Adobe ) it is stated that you can self-host the library. If I remember right (as I don't find the page anymore), it was also stated somewhere that you could run Launch on premise.
So, iss my memory correct regarding the on premise part:
It is not possible to run Launch entirely on premise. However, you can self-host your Launch library on your own system or any system of your choice. You do this by creating a Self-managed adapter. I've posted the documentation for this below:
There are a number of reasons to choose to host your own build files.
To meet these requirements, Launch allows you to push your completed builds to an SFTP destination.Launch connects to an SFTP site using an encrypted key. To use this connection type:
If you select an SFTP adapter for your environment, there is an additional path variable that you'll need to provide to the environment. This path field is the HTTP path to where your build files are stored relative to your web site. This field is required because the different files in the build reference one another. Launch needs to know where they will are so the files can reference each other properly.