I bet, the implementation of the pack is nearly as complex as it was for GtkRadiant 1.6.4.
Downlaod GtkRadiant 1.6.4 from icculus:http://icculus.org/gtkradiant/downloads.html#binaries
Unzip the file to a place you like.
Remove the unneccessary XXPak folders inside the folder called "installs".
You just need the folder "Q3Pack".
Start radiant.exe and select the game directory of you OA-installation.
Click OK and wait a few seconds. GtkRadiant will start and prompt you to select a game.
Just klick OK again and you will get the map editor. You have to quit for now, we will make the changes for oa before our next try ;-)
Inside the GtkRadiant folder you will have 2 more subfolders now:
games and q3.game
make a copy of the q3.game folder and rename the new copy as "oa.game".
inside of the folder you will find a file called local.pref.
open this file with an editor and search for "baseq3" and replace with "baseoa" (there should be just one place with "baseq3"!).
now make a copy of the file "q3.game" inside the "game" folder and rename the copy to "oa.game".
open the "oa.game" file and modify the quake related entries.
this could look like this:
<?xml version="1.0" encoding="iso-8859-1" standalone="yes"?>
name="OpenArena and mods"
now you have to have a subfolder inside the "installs" folder called "OAPack".
Just make a copy of the existing "Q3Pack" folder.
Inside you new "OAPack" folder you will find the subfolder "install".
he contains 3 folders, "docs" and "missionpack" can be deleted!
the subfolder "baseq3" has to be renamed to "baseoa" and inside this folder you have to delete some folders:
"maps", "models" and "textures".
you also have to delete the both files "common-q3map2.pk3" and "curry.pk3".
from the remaining file "common-spog.pk3" you just need the subfolder "radiant" with its files.
you can unzip "common-spog.pk3" and remove the "common" folder inside the newly created "textures" folder.
the texture folder also has to be put inside your oa game folder (inside "baseoa")!
now switch to your openarena directory and grab all files starting with with "PAK" andf copy them to the folder "\GtkRadiant\installs\OAPack\install\baseoa\".
next copy the following file from "baseq3\scripts" to "baseoa\scripts" inside you OA installation:
The user0.proj has to be modified: replace all q3 related path information to oa.
important: there should be an "OAPack" reference which also has to be modified.
next you can start GtkRadiant and enjoy mapping after the selection of OpenArena as your game.
important note: GtkRadiant seems to be unable to locate shaderlist.txt inside PAK0 properly.
so you have to make your own shaderlist.txt file and place it inside the "scripts" folder.
entities.def file could be used from sagos download.
It is not finished yet, maybe someone else likes to complete the guide and make a final package of his work.