This is national rails acceptable use policy.

Acceptable use Policy

Some individuals and organisations have been caught obtaining the data for commercial gain without being licensed to do so. Further, some users attempt to make excessive use of the site. While periodically refreshing browsers left open are acceptable, the use of scripts that draw down very high volumes of data is not permitted, since this jeopardises the service for other users.

We will detect and prevent such unlicensed activity to keep the service available for all our customers.


So by the looks of it, as long as its not for commercial gain, you dont need a license. Your advertising their company for free, and providing a facility which makes life easier for their customers. I think you'd need not worry, they'll be begging you to make it happen.