This library is merely a convenience for using ACE through tw2, all major credit goes to the developers of ACE. See also their repository at https://github.com/ajaxorg/ace
This package comes bundled with ACE from 11.05.2012, which is released under a BSD-3-Clause license. This package itself is licensed under the WTFPL, Version 2 (for the moment).
The directory ace-builds is a git submodule, but you don’t have to check it out if you want to use tw2.ace! It is only included as a convenience for updating the bundled libraries.