Forked from Lineage but it's unclear what problems are being solved that aren't already solved by Lineage.
Generally speaking you still depend on the device manufacturer to ship a compatible vendor partition in order to run a given version of LineageOS. This means that if your device doesn't have an official version of Android 8, then it will never be able to run LineageOS 15.
If your device doesn't already support 15, then it's highly unlikely that it will ever seen an official release with 15, or 16, or anything >14.1.
That is to say Duval based his product on whichever LineageOS release was 'current' at the time but plans to sync to the next available release when his next development cycle allows (which is Oreo, currently).
In other words, they're making the complete package and they plan to target average people.