According to the submission: "out-of-the-box support for community builds of Ubuntu Touch and Sailfish OS"

So even if it's not easily hackable or if MediaTek isn't famous for releasing kernel sources, seems like the company behind the phone will make sure at least Ubuntu Touch and Sailfish OS runs on it.

Edit: also, the sentence right your quote explains "In this case, however, Volla told us that its kernel sources should be publicly available"