From their site:

It is a complete solution for every organization to create, collaborate, share and publish all its internal and external documents.

You and your team can create and collaborate on:

• Text documents
• Spreadsheets (coming soon)
• Presentations
• Task Lists
• E-mails
• Calendars
• Web Links

All it requires is an xampp server (essentially a Linux server). I am going to test this with some colleagues and see how viable it is for a production environment, but on the surface it looks to be worth evaluation.

You can try a demo here. Once the spreadsheet function is available, this will become much more interesting.