I have been asked to help someone make a commercial Windows dll to do pocketing like in HeeksCNC. Unfortunately the polygon offsetting used in HeeksCNC is derived from the "kbool" software, with its' GPL license, so it has to stay free. I have done quite a lot of work recently to adapt the "Clipper" polygon clipping library to do offsetting too.
Here are my results.
The first picture was made using kbool.
The second picture was made using my modified version of clipper.