How to extract an .ace compressed file?
Shameless plug: With acefile there is now a python based solution to uncompress ACE archives, that is slow, but works on OS X.  Simply make sure you have Python 3 and then install acefile:

pip3 install acefile


Then you will have the acefile-unace utility installed, that you can use to extract ACE archives, including the newer ACE 2.0 format that is not supported by most archivers with ACE support on platforms other than Windows.  Run something like:

acefile-unace -x example.ace


You may have to explicitly give the bin path of your python installation if you don't have that in your PATH (e.g. /Library/Frameworks/Python.framework/Versions/3.4/bin/).