This is a layout engine extracted Apple Advanced Typography(AAT) implementation from ICU Layout Engine.
Some refactoring and many fixing bugs have been done.
Major functions of AAT which are necessary for shaping complex script such as Arabic, Devanagari, Thai, and so on, have been added.

On the other hand, OpenType implementations have been removed.

A new version of morx table was introduced, but it is not implemented yet.
Newly introduced functions are functions which can choose language-specific glyph, and improve performance of shaping.
Since new specification is designed with paying attention to compatibility, it can shape as well as before.

A kerx table which is a new version of kern table was introduced, but it is not implemented yet.

Features of morx table cannot choose. Default features are always chosen.

Any modifications and additions which are made to ICU Layout Engine can use under ICU License.