An essay, by me, on why open access and open education resources need open source:
The default file format for Microsoft Word is .docx, which is a not entirely open format. Right now LibreOffice, an open source word processor, can open those kinds of files, but what if Microsoft does something to change that? The “open” content will only be available to users who have paid for some sort of Word license. Can that content really be considered be open?