Think of SEBLOD as an extension to the standard Joomla article management system - it adds to it.
K2 on the other hand seems to want to replace it - instead using its own mini content management system.
You certainly can install SEBLOD together with K2 in the same website, but when you start learning how to use SEBLOD properly you may wonder why you even need K2.
I worked on a site a while back with K2 which I moved over to Seblod totally by exporting all the K2 content and importing it into SEBLOD Articles via the SEBLOD Importer.