> creative output such as artwork and music

If I'm not mistaken, all intellectual property published by the US government is public domain by law. I may be wrong or you may be referring to something else.

Close. It's not publication by the government that is important. It's authorship.

If a work is a work prepared by an officer or employee of the United States Government as part of that person’s official duties, then it is not subject to copyright in the US.

It might be subject to copyright in other countries, though.

If the government pays for a work to be created and published, but it is not a work prepared by an officer or employee of the United States Government as part of that person’s official duties, then it will be copyrighted and the copyright owner will be whoever it would be normally. If there is an agreement between the author and the government to assign the copyright to the government, the copyright will still be valid, and owned by the government.

I suppose you're right, but isn't that simply an issue of contract negotiation? Often when a private actor hires a contractor to create IP, part of what they're buying is ownership of the IP itself. I have no idea if the US government does this or not.

Freely redistributable artifacts are one thing, but publication "in the preferred form for making modifications" is a pretty important part of FOSS.

For most documents, copy and paste into a text editor is relatively straightforward. Highly technical documents are one obvious exception.

We're talking about "artwork and music", not text.