[nwah1]

Models I know of are open-core, dual-licensing, paid support, selling developer tools, and providing hosted cloud service offerings.

[beefhash]

Open core can go wrong if you're not coupling the valuable functionality tightly enough to the open core, though. This seems to be happening with BitWarden, where at least two free third party implementations of the password storage backend exist[1,2].

[1] https://github.com/jcs/rubywarden

[2] https://github.com/Odysseus16/bitwarden-go

[icebraining]

There's also custom development of modules/extensions to the core (it's not open-core because these developments may be open themselves).