There is no standalone product called Microsoft Office 2015 . However, Microsoft released Office 2016
: You can purchase a one-time license for Microsoft Office from Microsoft's official website or from authorized retailers. This option might not be available for every version, but it's an option for those who prefer not to subscribe. Microsoft Office 2015 Free Download 64 Bit
The Aristod company, which developed these tools, ceased its activities in April 2019, due to the very low interest that these tools have generated.
Jean-Francois Nicaud, the main author of these tools, keeps them available to users on this website for a few years.
Contact: jeanfrancois dot nicaud at laposte dot net