Here is a quote from Edward Fords blog:
I’ve looked high and low for a nice open source, entry level CAM program. As luck would have it, after YEARS of searching, I found one mentioned in another forum, and tracked it down to find out it had been abandoned but the source was released before said abandonment. It was created by a guy named Jack, and I’m planning to do an entire other blog post explaining how this came to be. For now, just know that Jack’s creation (which he called PartKam), is now available on my github page, and is being hosted at one of my other domains. You can find it here: www.makercam.com. You will find a basic ‘help’ and ‘tutorial’ link at the top of the page.