Microsoft has established the
Open Specification Promise, which allows developers and customers working with commercial or open source software to be able to implement specifications through a simplified method of sharing of technical assets.
These specifications include the Virtual Hard Disk (VHD) Image Format Specification, Office XML File Formats, Security specs (like the Sender ID E-mail Authentication) and numerous Web Services. For a complete list, along with FAQ and Community Representatives' feedback, please visit this web page:
Microsoft Open Specification Promise