I think the key issue here is that when a government imposes administrative procedures on its citizens (e.g. tax returns), it should be entirely logical for said government to provide free software that reduces the administrative load. In fact, this should be the norm. You can't accuse the state of anti-competitive behaviour in this case, because the market you're serving wouldn't even exist if they hadn't created tax filing procedures to begin with.

Or, as I like to think of it, governments, by necessity, introduce a certain amount of friction into our lives, and have every right to try and reduce that friction. If your business is built on reducing that friction, you simply need to ensure that your service stays ahead of the free service, because your profits are not a right.