You could try setting up LibreOffice Online, but it's quite a big job, and I'm not sure if you can easily limit editing in such a way.
On a smaller scale, there's WebODF: http://webodf.org/about/features.html – but I think that can only display spreadsheets (editing only appears to be available for text documents).
Heh, I guess reimplementing LibreOffice JavaScript would have required a much bigger effort. That said the Document application for OwnCloud uses WebODF which pursues exactly that approach, I don't know how much faithful their document rendering is though.
It's just a matter of taking different approaches with different tradeoffs.
Have you even looked at these? All are horrible!
Not updated since 2010. PHP errors on the fucking homepage! >http://webodf.org/apps/
No editing. >https://itunes.apple.com/us/app/documents-unlimited-suite/id504968354?mt=8
Unusable horrible user interface. It's a front end to a remote instance of Libre Office running on a server! I could run remote desktop and have the exact same experience.