The DLC installers for OSX that are included with the Kickstarter edition 1.6.4 are installing their payload into the wrong location.
Instead of into "<install dir>/War For The Overworld/WTFO.app/Contents/Resources" (inside the application bundle) it is put into "<install dir>/War For The Overworld/Contents/Resources" (besides the bundle).
No, I had to copy it in.
--- (The following is me still being in "at work" mode, oops)
BTW: Those installers (including the main one) are really weird. They ask for admin rights, run through the whole installation procedure and then ask for a folder with no indication what it will be used for, defaulting to the personal Documents folder. Looking into the PKGs I see that the installers don't actually do anything at all, the complete installing is handled by the postinstall script.
Also, the game is storing its settings and savegames inside the app bundle. That's a bit of a maintenance nightmare. OSX user expect to be able to delete the app bundle without losing data (savegames!). This may be a relic of the porting, but even on Windows you don't store savegames in "C:Program Files"...
My recommendation for a quick+easy "make it as users expect it to be"-fix would be:
1. Deliver the game itself in a DMG. It's just a single app bundle, it doesn't need an installer.
2. Change the game to expect all files it writes (settings and savegames) and the DLC files in one folder: ~/Library/Application Support/WFTO" (This is the big change...)
3. Change the DLC pks to install into "~/Library/Application Support/WFTO" without asking for root or a target folder. (or "/Library" to install for all users, but that ones does need root access and I found entering the root password 8 times more annoying than doing the installation multiple times if there are multiple user accounts that play WFTO would be)
oops, sorry for the typo in the title. "osc" -> "osx"