I do agree with everybody that the license only allow to use the Esu files with Esu decoders. Paragraph 1.3 only describes that you can add data to the file (and remove from it) and that you can distribute it, but not that it can be used in a third party decoder. This is exactly what happens with for example companies in the UK selling ESU decoders with their own adaptation of the ESU files.
And even if this wasn't the case I do agree that ethics would require you to use it only with ESU decoders. They put a massive amount of work into these recordings and we all benefit of that work.
Marc
