You searched a paid product
Box does 3 jobs: desktop file sync, file sharing links, browser access to files. Most projects replace one or two of them, so pick the job you actually need.
Open-source alternatives to Box that run locally, allow commercial use and need no paid API include OpenCloud (desktop file sync, file sharing links and browser access to files; Apache-2.0; runs on CPU). Nextcloud Server, OpenCloud and Seafile cover all 3 Box jobs.
Self-hosted file sync and share server with desktop and mobile clients, share links, file versions and an app store for calendar, contacts and more.
Apache-2.0 file sync and share server (community continuation of oCIS) that stores everything on the filesystem with no database; Docker install.
Self-hosted file sync and share with selective sync, encrypted libraries, share and upload links and version history; Pro edition free up to 3 users.
No project meets all of your requirements. The list below shows what you'd need to relax.
We hid them because something is missing, unknown or conflicting. Here's what.
Yes. Nextcloud Server, Seafile and OpenCloud are free to download and run on your own computer without paid API keys. Each covers every job we list for Box.
Yes, with Nextcloud Server (AGPL-3.0-or-later), Seafile (AGPL-3.0-only) and OpenCloud (Apache-2.0). Check the hardware notes and licence conditions on each page before you start.
Yes, with Nextcloud Server (AGPL-3.0-or-later), Seafile (AGPL-3.0-only) and OpenCloud (Apache-2.0). Check the hardware notes and licence conditions on each page before you start.
Confirmed: OpenCloud. With conditions: Nextcloud Server and Seafile. This is not legal advice; read each licence.
Nextcloud Server, OpenCloud and Seafile cover every job we list for Box.