With the release of the latest version of Microsoft Security Essentials 2.0 in December 2010, Microsoft also changed the licensing terms.
Small Business. If you operate a small business, then you may install and use the software on up to ten (10) devices in your business.
Now although 10 PCs isn’t a lot, some Administrators might be interested in configuring their Microsoft Security Essential clients with a GPO. Fabien Duchene has created an Administrative template for MSE. Read more here
UPDATE:
Just came across another great blogpost about GPO and MSE check it out here:
http://www.grouppolicy.biz/2010/09/group-policy-for-microsoft-security-essentials/