Can someone explain how magnetic potential energy can exist even though the field is non-conservative? $U=-B\cdot \mu$ is defined to be the magnetic potential energy, I saw this in my lecture notes, but we had already talked about the fact that since the work done to move a charge there is path dependant, there can not be a unique potential at a point in a magnetic field. So there is no use in defining a magnetic potential energy. 
The only thing I have in my notes is that it shows for a current loop, it has the most potential energy when the magnetic moment is perpendicular to the field, and has 0 potential energy when it is parallel. I can sort of justify this by saying it makes sense that the potential should be a maximum in an orientation where there is the most restoring torque on the loop and minimum where there is none
But what does a potential mean in a non conservative field?
 A: The problem you're having is that your confusing a field's scalar "potential" with potential energy. The concepts are related, but in a particular way. Say I have a vector field $\mathbf{V}(\mathbf{x})$. There is a mathematical theorem that I can break this field down into two two parts
$$\mathbf{V}(\mathbf{x}) = -\nabla \Phi + \nabla\times\mathbf{A},$$
$\Phi$ is something we call $\mathbf{V}$'s scalar potential and $\mathbf{A}$ is its vector potential.
The connection to potential energy comes in if we can write a force on some particle is of the form
$$\mathbf{F} = a \mathbf{V}$$
and $\mathbf{A} = 0$, then the potential energy of that particle will be $U = a\Phi$. 
So, in the case you're dealing with you don't have a force of needed form, so it's not a problem. Granted, we still have the statement, "The magnetic field can do no work," but showing how that works out in the case of a magnetic dipole like this is subtle. In fact, the force and torque on a magnetic dipole are
\begin{align}
    \mathbf{F} & = \left(\mathbf{\mu}\cdot\nabla\right)\mathbf{B} \text{ and} \\
    \mathbf{\tau} & = \mathbf{\mu}\times \mathbf{B}.
\end{align}
I'm less certain here, but I'm pretty sure you'll find that the combination of those two makes it impossible to harvest infinite energy from any static magnetic field. 
