I heard that the judge was hiring an amicus to provide a more adversarial position because the government and the accused seem to be in a bit too much agreement. I would assume the amicus is going to be on the prosecutorial side. I'm not sure if that is the same as a special prosecutor, but it sounds similar.

That's a different role. The judge has asked for a third party to argue the contrary position on the motion to dismiss the prosecution. This happens from time to time - for example, last month SCOTUS appointed outside counsel in two cases where the Court had granted cert but the government had elected not to defend the lower court decisions:

scotusblog.com - Outside attorneys appointed to argue in two cases

Judges rely on the work of competing, adversarial counsel to give them a full understanding of the issues in a case - so if for some reason the two parties end up supporting the same position, they will look to outside counsel to brief the other side so they have the benefit of that perspective.

But that's a very specific and discrete job, preparing for a single argument on (typically) a single issue to be resolved in (typically) a single hearing. Being a prosecutor in a public corruption case is a much larger task, which usually requires a full team of lawyers that have the resources of a prosecutor's office behind them.