An enterprise note-taking collaboration system?

Question

Notes

I want a corporate note-taking system.
Basic requirements
* collaboration, the server part should not be on the Internet, but on its own server
* offline client (that is, work not (not only) from a browser, but also from some offline program
* a simple WYSIWYG editor, this important - there should not be any manual wiki markup outside (for users) (but inside wiki or markdown is just welcome - the simpler the better; however, what will be inside does not matter). standard - headings, tables, pictures, bold-italic-underline
* multi-level notes tree (for example, evernote has only two levels, you need a lot)
* preferably open-source
As an option, instead of working through a central server, an offline-outliner option is considered with storing each note in a separate text-based file, and putting it all under the version control system. The rest of the requirements are the same.
Is there anything similar?

Answer 1

check Outwiker