Licensing
The product's license agreement allows home users to download, install and use it on an unlimited number of computers in their households free of charge, so long as each computer has a legitimately licensed copy of Microsoft Windows. Since October 2010, small businesses have also been allowed to install the product on up to 10 devices, but use in academic institutions and governmental locations is forbidden, as is reverse-engineering, decompiling or disassembling the product or working around its designed limitations.
MSE requires no registration or personal information to be submitted during installation; however, the validity of the operating system's license is verified during and after installation using the Windows Genuine Advantage system. If said license is found to be invalid, the software will notify the user and will cease to operate after a period of time.
Read more about this topic: Microsoft Security Essentials