No, whether or not God is moral would have nothing to do with it. The goal of human ethics is to minimize human suffering, regardless of whether God exists or not. If it is the case that God will punish one in hell for all eternity for homosexual acts, then one ought to avoid homosexual acts in order to avoid the suffering that they will bring. The right action is the one that has the effect of minimizing suffering. Even if God is moral, that doesn't make obedience to him obligatory or ethical. What makes it the right or wrong course of action is its consequences.
Imagine a world in which God is good/moral, but where He eternally tortures humans that obey His commands in hellfire. In such a world, obeying God would maximize suffering rather than minimize it, so disobedeying God would be the right course of action.
All moral obligations stem from hypothetical imperatives. The notion of a categorical imperative is basically incoherent in itself. What's good is neither supernatural nor absolute. What is good is a matter of preference, a matter of preference that humans generally agree on I might add—what's good is that which we desire (self-preservation, comfort) and what's bad is what we wish to avoid (pain, anxiety, discomfort) and these preferences are mostly biologically determined so that all humans agree on them. Human ethics is grounded in human nature. God could not possibly be moral in the human sense of the term. For humans, cruelty is wrong because suffering is bad by definition—i.e. we define "bad" as something that we dislike, something that increases our suffering. God is supposedly impassible (i.e. incapable of suffering), so he cannot naturally suffer, and so cannot naturally view cruelty as bad... You cannot sympathize (suffer with) others if you do not know what it is like to suffer. The concept of cruelty being immoral would be impossible given God's nature. God can't sympathize because He can't suffer, and so such a being can't possibly be morally good in any sense of the term that is coherent to humans.