At first glance looks like your WT3020H uses a different SoC (MediaTek MT7620N). The GL-AR150, on the other hand has, apparently, the same SoC than the pineapple (Atheros AR9331), so I bet you cannot proceed as per the link you found.
You can get the pineapple firmware and extract it (using the tool mentioned in the link or
binwalk -e). Then copy one of the binaries (and maybe some libs) into your OpenWRT router and try to run it. If it works then, you may have a chance...
I do not own any of the mentioned devices so I cannot really say much more
Hope this helps