Apparently, administrative permissions and the name/URL. In this case also the dev. As it's under MIT-license, they can't buy the software itself, but they can control the public appearance and merges, until someone forks it and becomes more successful.
> As it's under MIT-license, they can't buy the software itself
This is a common misconception. Just because the author or original IP owner chose to release it under MIT doesn't mean they no longer own it -- and if the company wants to acquire it they can. They can never remove-from-the-internet the existing MIT-licensed versions (though they could take down their own copies), but being the owners they could certainly decide to release future versions under a different license.
I don't know why they'd report on it in startup-speak like this, I doubt investors will care. Must be an ad.