It's a sexy name by some middle manager somewhere, or some executive3 that got a good idea while taking a morning duce, to come up with an exciting new project that will juice their resume and hopefully get them promoted before it comes to the front that they do nothing and their objectives are entirely fluff.
It's an old trick first called out in The Dilbert Principle that you get promoted by being associated with sexy sounding projects, the best case is a sexy sounding project that has vague objectives.
Given the blurb above it sounds like there is very little substance to this and lots of style. Expect it to be sunset or fade into obscurity in 3-5 years.
EDIT: For context their stated mission is
> GitHub Next investigates the future of software development.
We explore things beyond the adjacent possible. Tools and technologies that will change our craft. New approaches to building healthy, productive software engineering teams.
Notice the lack of anything that will actually be produced, key words that you are dealing with BS is "explore", "approaches", and "change our craft" without any details on what any of that means. If they were producing or doing something they'd say that. As is it's meaningless marketing drivel that could translate better as "We've made up a fake job to play with cool tech, write ill-informed meaningless blog posts about what the next cool thing everyone should do is. We're also light on technical skills so we are going to focus on teams and projects not actual tech"
I don't begrudge them the fact they weaseled their way into this job good for them, but I don't expect much, and If I am wrong and these are actually super smart talented individuals that finally got the freedom to make something happen then I apologize for my dismissiveness. That being said when companies get acquired by MS they don't tend to be known for their innovation and ground breaking research going forward.