This option is available to communities who would like to host a site using their own hosting setup and don't want us to backup, upgrade, or otherwise maintain the site.
Currently we recommend using an account at https://www.opalstack.com The email lists in Mosaic work with opalstack's API but could be adapted to other hosting environments.
Instructions for installing and building a site yourself can be found on the Install and Build page.
Please contact us for more details.