Hi Mark,
Thanks for reaching out with your Total Upkeep questions! Unfortunately at this time there’s not way to backup all sites on your server within a single instance so you would need to install the plugin on each individual website.
As far as your number of installations since you InMotion Hosting, one of our premium service partners, you have unlimited access to your BoldGrid license key so you’ll have no trouble implementing the plugin on each site.
I hope this helps Mark! Please let us know if there’s anything else we can answer for you.