To be fair they explicitly state don't use their branding in the API documentation. They made £200K in 2024 from licensing - I think about a millionth of a penny per journey
https://content.tfl.gov.uk/tfl-advertising-annual-report-202...
https://content.tfl.gov.uk/tfl-advertising-annual-report-202...
That seems very little to be honest. Who is licensing what from the London Metro?
https://tfl.gov.uk/info-for/business-and-advertisers/contact...
There is no way they are running a licensing department for under £200kpa.