I dont know about the VMG1312, but I could access my VMG8324 using my ipad/galaxy tab - neither have java.
Everything seemed to work ok, but then again I didn't do much configuring in it because things like that are best done via a keyboard rather than a small touch screen.
From what I have seen the GUI interfaces between the 2 are very similar, except the VMG8324 has an additional (javascript) popup menu for VoIP. You definitely need javascript.