I think you can try starting mod from System.
1) copy postal2.exe as postal2CoOp.exe
2) copy postal2splash.bmp as postal2CoOpSplash.bmp
3) copy Postal2CoOp.ini to /system folder
4) open ini file and change postal2.exe to new one (see s.1)
5) try to start new exe

Evil that those type of files are only Windows.

On Mac they are .int files.

I'm mainly wondering if this mod outright doesn't work for mac or if I can jerryrig something together in order to get it to work.

@fifthstone,
For some reason P2 on mac can't restart game from code.
Anyway, try my previous solution. To start from /system game needs 3 files
1) postal2CoOp.*executable file (same as postal2 executable original one)
2) postal2CoOp.ini from
...\steamapps\common\POSTAL2Complete\WorkshopContent\737631813
3) postal2CoOpSplash.bmp (same as postal2Splash.bmp)

Place these files in
...\steamapps\common\POSTAL2Complete\System

I've been doing what you've suggested, and this is the error I'm getting. Also I'm sorry if I sound grumpy, so just letting you know that you're doing awesome work and I have nothing but respect for you.
Process: postal2-bin [2360]
Path: /Users/USER/Library/Application Support/Steam/*/postal2CoOp.app/Contents/MacOS/postal2-bin
Identifier: com.runningwithscissors.postal2steam
Version: ???
Code Type: X86 (Native)
Parent Process: launchd [184]
Responsible: postal2-bin [2360]
User ID: 504

Date/Time: 2016-08-12 23:42:52.527 -0700
OS Version: Mac OS X 10.9.5 (13F1507)
Report Version: 11
Anonymous UUID: 98803402-1114-4F1C-F1CD-94CFB62C2FE4

Sleep/Wake UUID: 5B73B1B8-8537-43F4-B057-15324F4CE13B

Crashed Thread: 0

Exception Type: EXC_BREAKPOINT (SIGTRAP)
Exception Codes: 0x0000000000000002, 0x0000000000000000

Application Specific Information:
dyld: launch, loading dependent libraries

Dyld Error Message:
Library not loaded: @loader_path/libSDL2-2.0.0.dylib
Referenced from: /Users/USER/Library/Application Support/Steam/*/postal2CoOp.app/Contents/MacOS/postal2-bin
Reason: image not found

Originally posted by fifthstone:

Reason: image not found

Looks like no loading image
In Windows version it should be postal2CoOpSplash.bmp, but in Mac..
Probably postal2Splash.* image have different format?

My main problem right now has nothing to do with the mod and now involves finding out A: Where the Postal 2 frameworks are located, and B: to learn where the postal2-bin file gets it's data(because it's not from the system folder) and adding the launch image to that. Also the problem goes for all of the Postal 2 gamemodes, not just postal2CoOp, meaning that Postal 2 and Postal 2 Paradise Lost suffer the same glitch at launch when you try to open them from the files. Anyways, thanks for the help, although it seems the game breaking bugs have nothing to do with the mod at this point in time.

@fifthstone,
Did you find postal2.ini config file?
If yes, the last solution (not best, because you will be need to replace config files, every time you launch original p2 or coop mod):
1) backup your postal2.ini
2) replace it with postal2CoOp.ini (just rename it to postal2.ini)
3) launch P2 via shortcut or steam

Hope this will work.

Right after i start default map with NicksCoop, it crashes (Mac, El Capitan 10.11.5) I don't know much abbout computers but im trying to make that work

This worked for me Evil, thanks!

Originally posted by fifthstone:

This worked for me Evil, thanks!

Ok, good to hear that >)

Originally posted by RulingChicken:

Right after i start default map with NicksCoop, it crashes (Mac, El Capitan 10.11.5) I don't know much abbout computers but im trying to make that work

Try previous solution.

In detail:
1) Make a backup for main config file:
...Steam\steamapps\common\POSTAL2Complete\System\Postal2.ini
2) Copy config from:
...Steam\steamapps\common\POSTAL2Complete\WorkshopContent\737631813\Postal2CoOp.ini
Paste it to: ...Steam\steamapps\common\POSTAL2Complete\System and rename into Postal2.ini
3) Launch game via steam/shortcut
P.S.To launch the regular Postal2 again, you need to delete the coop config and replace it with backup one.

Hi! I tried to do your last solution which apparently worked for another user, but I can't find a Postal2.ini in my System files. Would you recommend another solution maybe? Thanks!

Originally posted by uccakiroglu:

Hi! I tried to do your last solution which apparently worked for another user, but I can't find a Postal2.ini in my System files. Would you recommend another solution maybe? Thanks!

Have you found it?