It's well-known that any one dimensional formal group law over a $\mathbb Q$-algebra or a reduced ring is commutative, but there are one dimensioal non-commutative formal group laws over rings like $k[\epsilon]/(\epsilon^2)$, where $k$ is a characterestic $p>0$ algebraically closed field (for example, take $F(X,Y)=X+Y+\epsilon XY^p$).
It's easy to classify one dimensional commutative formal group laws over $k[\epsilon]/(\epsilon^2)$ up to isomorphism by deformation theory. How about non-commutative ones? In other words, what is the full classification of one dimensional (non-commutative) formal group laws over $k[\epsilon]/(\epsilon^n)$ $(n>1)$ ?
