You can use OS OpenData map datasets in any way and for any purpose.
But you must acknowledge the copyright and the source of the data, as follows:
Contains OS data © Crown copyright and database right (year)
If you use Code-Point Open data, you must also display the following:
Contains Royal Mail data © Royal Mail copyright and Database right [year]
Contains National Statistics data © Crown copyright and database right [year]
OS OpenData is free to use under the Open Government Licence (OGL).