that page is PR lingo telling exactly the same thing i said..
the first line even say: in doubt use gitlab ee
the point here is that core has two distinct meaning in the op question in gitlab pr..
Gitlab ee is their core product, core here meaning their main product..
the fact that the core of that product, here meaning the base the product is built upon, was released as open source does not make the whole product open source..
So, gitlab core\main product is not open source.. But the core\base of that product is..
They do have gitlab ce that has just a subset of the functionalities from Gitlab Enterprise that is open sourced.