system 7.0 was the last version of the macintosh operating system that was available for no charge and could be freely redistributed. although system 7 could be purchased from apple, the cost was nominal and considered to only cover duplication and media. it was common for macintosh dealers to allow customers to use the store's demo machines to copy system 7 install disks for the cost of a box of floppies. cd-rom magazines such as "nautilus" included system 7 on their disks. after mac users downloaded thousands of copies of system 7 from the online services (aol, compuserve and genie), apple surveyed the services and based on this popularity started selling the mac os as a retail product with system 7.1. apple continued charging for major operating system upgrades until the release of os x mavericks in 2013.