You can already download a local version. That is the full source. Download it, inspect it.
He is working on a github release which will be licensed 'open source', as stated in the proposal, that will be spring next year. I have no reason to not trust him.
It is minified and obscured last time I looked.
https://unminify.com/
On mobile but usually you are still stuck with poorly named functions and variables making it a nightmare to work with.
It looks ok to me, and the confusing function names could also pop up in 'well documented' code :)
Bottom line: the source is accessible.
I was not even aware it was minified like this, though. It will be on github soon under what I understand is an open source license - that was my main point.
edit: well, I looked at it again and it is not readable. Still, I have no reason to doubt it will be open sourced soon.