pkk is short for partiya karkeren kurdistan, which in kurdish means kurdistan workers party. they're definitely not liberal, not in the name and not in practice. but the ways they operate is always "icky". their actions regularly align with the us hegemony. "kurdish problem" has always been an important issue in turkey, and for the last 40 years pkk has been the dominant force to agitate that.
that terrorist list is just a tool for imperialism. you can see it clearly in the yemen situation, they got out of the list and got right back in. it's basically carrot/stick for the relations between turkey.
what i mean by aligning is: they are an insurgency, so their fight can be a catalyst for totally different projects, as we saw in libya. but sometimes they really do some stuff that benefits both themselves and imperialism, even though it hurts the proletariat.