I have some LEGO Commando Droids. The torso, head and arms are original with the LEGO logo, but the legs have no logo. They do however have numbers on them (here 2, on others 4 or 3) The legs are in terms of form and material identical to the original legs.
It seems unusual that somebody would go through the effort to fake the legs but not the rest of the droid.
It also not uncommon for official LEGO parts to exclude either a part ID or LEGO copyright stamp, this could be because the part was manufactured before it was the standard but most likely through design considerations.
It looks like there are no flat/continuous surfaces where either of these markings could be made legibly and without spoiling the characteristics of the part.
Looking at the pictures of this element I found that some, probably early version, indeed have a part number in plain visibility. Sometimes when mold worn out and LEGO makes a new one they could update the location of the marking. Making it far less visible and using hair thin text.
I don't have this element to tell for sure if this element is fake or not. However, I could suggest couple of other places to look for. First, the most obvious one - check if logo and/or part number haven't moved to the very bottom of the legs (the under stud part of it).
Next option, which is a little more interesting and not as obvious, might be already seen on one of your pictures (below). Picture is a little fuzzy, but the shading tells me there could be some text rotated counter-clock wise.