It is all about personal liberty, about giving people the right to take someone else's creations, change them however they see fit, and do whatever they want with them, including re-sharing them.
That doesn't sound very left wing to me because, in software, copying does not remove the original, meaning limited intervention by government is needed to protect those rights. All the state need do is refuse to participate in legal action undertaken by those trying to trample on others modifying the code. At most, I would argue that state intervention might be needed to compell the release of source code, if mandatory source code release forms part of the mechanism.
That said, that doesn't mean it's inherently bad (as a consequence of being 'left' or 'right'). I think trying to put everything you agree with on the same side of the spectrum that you self-identfy with (and, conversely, putting everything you disagree with on the other side) is harmful to the people because it hinders bipartisanship on universally good ideas and enables malfeasance by leaders in an aligned party.