That would be more like an Apple device.
Generally speaking, only apps from the store can be installed on the Win RT version of the Surface. The Surface Pro, which will feature Windows 8 (not RT) but isn't out yet, will be able to install applications that also run on Windows 7.
There will be, however, a way for organizations to deploy applications to devices associated with them (through Active Directory), without publishing on the Windows Store. An April 2012 post on the Building Windows 8 described this.