looks like it's possible to get support for the z-sticks by compiling the kernel modules - though OpenHAB is asking a bit much of the lower-end openwrt routers since it uses a full JVM, you'd probably be better off with Domoticz (though it's not as feature rich). Or just get a Pi2. Would be super interested if anyone gets either of these running in asuswrt for sure.
I agree - a Pi 2 is probably a better choice - Raspian is a richer environment for general usage than OpenWRT (or AsusWRT for that matter) - not better or worse, just different purpose.