Both of those statements are not strictly true, though there's plenty of truth to them.
UL approval is not required in all jurisdictions. It tends to be a city/county level affair. Many larger cities tend to want it, while smaller areas tend to not care. Many of those locales also permit CSA or similar approval which tends to be a little cheaper/easier to attain (the standards are often identical). Some insurance policies will require electrical equipment on a commercial premises be UL or CSA approved, but I've not found it common. I know many establishments with tons of non-UL recognized equipment.
FCC Part 15 has exemptions for stuff made in extremely low quantity (I think the number is 5 units or less, but don't quote me on it). FCC Part 15 approval can be obtained for about $800 at a discount lab, if you need it, assuming you don't have any problems. You'd only have to meet class A for commercial usage, which is pretty lenient. Most off-the-shelf equipment you'd use to build a homemade jukebox (e.g. the PC, amp, etc.) will likely have been designed to the stricter class B (residential) requirements, so you won't likely have a ton of problems, but anything can happen.
I suspect the patent minefield and music licensure nightmare would be bigger issues, but if you live in a jurisdiction that requires UL acceptance, then you're pretty much screwed as that can be a nightmare to obtain if you've never done it before.
Of course, I still maintain that while it may be possible to do this, it's just plain not worth it. Stick to putting stuff in your basement.