Since 2009 Microsoft’s Code of Conduct has been applied to more and more of their online service. If a service is covered by this Code of Conduct, users of it are prohibited from using it in “any way that promotes or facilitates the sale of ammunition and firearms” (See bullet point #13).
Almost all of Microsoft’s online services are by now covered under this “Code of Conduct”. These services include Windows Live, Office 365, Microsoft Sharepoint, Bing.com, Outlook.com, Windows OneDrive, Exchange Online, MSN and a number of other services.
The only major Microsoft services this does not apply to is, at the time of this blog post, Skype, Microsoft Azure and XBox Live. I expect Skype will eventually fall under the Code of Conduct.
Windows OneDrive, formally known as Microsoft SkyDrive, is built into Windows 7, Windows 8, Windows 8 for Phones and Windows 8 for Tablets.