… I would like to use the jazz font that's in Finale 2010, which I still use after all these years but can't find in updated versions …

If I understand you correctly, you are still using Finale 2010 (after all these years) - right?

Are you saying that you can not find the Jazz font in the Finale versions 2011, 2012, 2014, v25, v26 ?

As Far As I Know, you still get the Jazz font when you install any of these Finale versions.

… Any way that can be authorized? …

There is no need to authorize a font.

Just install the font, and you can use it.

You could e. g. install the Finale demo.

When you have done so, you have the Jazz font in the Fonts folder - and you can use the font in any program