Oh I totally forgot our conversation about webODF. Document editing goes trough Java (Tomcat server) and use LibreOffice for conversions like exports to PDF, HTML, (CSV, XLSX) or (DOCX). They supported powerpoint presentations too but currently I dont see ppt support anymore. SpreadSheet works almost like LibreOffice version so you dont need install any office system to PC stations. First I wanted use just framework to integrate this functionality info GO but currently it almost looks like they are going to rewrite all parts to Ext 4 so the best is open document in this app. It will work almost same like editing in Drive - but you dont need upload file outside your server.
IT Analyst, Independent seasoned Group-Office developer, Educator of web applications