I'll caveat this post with the advice that you should wait for an official fix, don't blame me if it goes wrong, I'm not responsible for global warming, etc, etc
With that being said, for the brave among you, here's a fix. Essentially it fixes up the @rpath of the binary and copies in a missing steam library.
For this to work, you will need an existing steam game installed. Also note, copying and pasting from here may not work so I advise you paste into a text editor then re-copy from there.
cd ~/Library/Application\ Support/Steam/steamapps/common/Spriter/Spriter.app/Contents/MacOS
install_name_tool -add_rpath @executable_path/../Frameworks/ Spriter
cd ../../../..
find . -name "libsteam_api.dylib"
At this point you should see a list of paths to the steam library. I only have one other thing installed at the moment so for me it was this:
./Sprite Lamp/SpriteLamp.app/Contents/MacOS/libsteam_api.dylib
Copy this file into the Spriter directory, making sure you put double quotes around the path if it has spaces (probably best practice to add them anyway)
cp "./Sprite Lamp/SpriteLamp.app/Contents/MacOS/libsteam_api.dylib" ./Spriter/Spriter.app/Contents/MacOS/
Relaunch from Steam. Profit!
Let me know if you have any issues and I'll try and help as best I can. Merry Christmas!
