update (19 March 2014): Just to confirm it: Nelson Mandela Centre Of Memory is free of charge, but by appointment only. Be sure to book well in advance.
update (18 Nov 2013): According to the BBC, the Nelson Mandela Centre Of Memory will open to the public in the first week of Feb 2014. It will be free of charge, but visitors will have to book online first.
The current President of the Republic of South Africa, Jacob Zuma, will today (18 Nov 2013) officially open the Nelson Mandela Centre Of Memory public facility and the permanent exhibition on the life and times of former President Nelson Mandela at the Nelson Mandela Foundation in Johannesburg in South Africa. The Nelson Mandela Centre Of Memory will be launched as a public facility that bears testament to the living legacy of former President Mandela.
The Nelson Mandela Foundation is located in 107 Central Street, Houghton, Johannesburg. We'll keep you posted regarding opening times, entrance fees etc.