Sombody in there understands something about Free Software...
given that the API is under the Apache license:
so there are clearly some people with some sort of clue involved, but apparently the higher-ups don't understand that requiring a secret developer key is a show-stopper when it comes to a Free Software client implementation.
I also find it pretty odd that they appear to have written an API without a reference client to go with it -- how are they testing this stuff? (or is there a secret in-house client for testing? If so, shouldn't taxpayers get access to that too, having paid for it?)
This seems to amount to something akin to illegal state aide of the proprietary vendors to me. The cheapest that one seems to be able to get bridge software for is about 75 quid, and the cloudy offerings are charging a tenner a month or more. If one multiplies that by the number of VAT registered folk that need to comply one is talking about a vast cash injection for the accountancy industry for what amounts to almost no gain and often quite a lot of pain for the people that are actually doing something productive.