In a surprise move, Sophos Anti-Virus for Mac Home Edition is now available free of charge. I’d guess they are doing this to increase their market presence.
The Sophos Anti-Virus for Mac Home Edition uses the same engine as the commercial version of Sophos Anti-Virus 7.2, but has an easier to use interface. There isn’t any information on Sophos’ website regarding if it’s legal to install this on commercially used Macs, but for what it’s worth there’s nothing that would stop you from doing so. http://www.sophos.com/products/free-tools/free-mac-anti-virus/