It comes preinstalled with a selection of the most common free multimedia applications available.
When Linux projects say "free" they usually use that word to mean F(L)OSS rather than "at no cost"; there's a "thing" in Linux culture about "free as in beer vs. free as in freedom" and just because software is provided at no cost doesn't mean it's actually "free," etc. In fact, the word free in the text you quoted is a hyperlink to the wiki explanation of free as in freedom software/FOSS/FLOSS:
https://en.wikipedia.org/wiki/FLOSSSo anywhere you see the phrase "free software" in a linux context, it's often a good bet to just read "F(L)OSS." They go on to clarify that
FLOSS stands for Free Libre Open Source Software. With some minor exceptions, such as non-free wifi drivers in the kernel, all the applications you use on Ubuntu Studio are truly FLOSS.
So JRiver would probably be ideologically excluded even if they were willing to bundle it (which they probably wouldn't be).