Hi Matari, and welcome to Roots Chat.
I'm afraid you have a few misconceptions........
The National Archive has not been sold off. Whereas all the previous censuses have been microfilmed in the past, the 1911 census has only ever existed on paper, so to make it available online, someone has had to photograph, digitise, transcribe and index the entire collection which takes nearly a mile of shelving to house in physical form. This operation was beyond the current capabilities of the National Archive, so a company called Brightsolid, which owns (amongst others) the Find My Past website was invited to collaborate with the NA to do this work. In return, Brightsolid has the rights to operate a Pay As You Go access facility, and it has sole rights to the data for an agreed period. Later on, other companies will be able to access this data too. Obviously Brightsolid want to make a profit on the money that it has spent doing a lot of work to make the 1911 census available online.
The "100 year rule" that you refer to was only passed in 1921 with the Census Act, so it does not apply to the 1911 census. However, certain personal details (like infirmities and disablities) will not be readable until after 2011.