Well.. would you look at that. More mystery errors!
Edit: Fixed with 'brew link sdl2'
Will attempt to try latest builds again
EDIT AGAIN: LATEST OPENJK WORKING!
ANOTHER EDIT LOL: LATEST BUILD OF JA++ WORKING! Dylib files need to be placed in japlus folder with the pk3's, not in a separate folder as its downloaded.
For future reference mac owners, install Homebrew. Then, in terminal, type
brew install sdl2
If it says its installed, but not linked type...
brew link sdl2
Dragging and dropping the sdl2 framework into the framework directory alone won't work!
elias's post in OpenJK (OSX) SDL2 Issues was marked as the answer