If you are an existing owner of a perpetual license, you can generally still use the software, but new users will find that official support and installer hosted on Autodesk’s main site have been removed. Where to Look for the Installer
To understand the demand, you must understand the software’s timeline. ArtCAM 2009-2011 represented a “golden era” of stability and performance. Here is why 2011, specifically the 64-bit version, remains popular: artcam 2011 64bit link