Just to be 100% clear. Corona does not officially support running in the background. Can you launch the Apple Music App? Sure. Can your Corona app play audio in the background. Not officially. There is an assumption that any Corona display items be in the foreground for them to work.
To be 100% clear on a second point. We have API’s that can read a file from a URL and start playing it before it completes downloading. When we stay streaming this is what we are talking about. However if you have a feed that produces continuous audio, not a distinct file, then no, we cannot play those types of continuous streams.
It may be possible to do this with native. iOS does internally support background audio and using some non-documented, non-supported API’s you may be able to get audio to play in the background since no UI is needed. However if you want to have a mini-player on the lock screen, you will want to do native builds for this. Android will of course be considerably different for this. We certainly don’t have those hidden API’s for background audio available on Android.
You will have to be the one to decide how much common Lua/Corona code your app can share before you decide if you want to pursue using Corona Native, or just go 100% native to do what you want.
Finally plugins in the marketplace come in three types: free, a one time only fee, and annual fees. I’m assuming you’re talking about a plugin with an annual fee. As long as you are providing updates to your app, you would need to be subscribed to the plugins. 17 years is a long time to plan to manage an app in the app store.
You should always figure the cost-benefit analysis for any thing you choose to pay for vs. doing the work yourself. If a plugin costs you $20 a year, how many of your work ours does it take to cover $20 of your time? Does the paid item (plugin, artwork, audio etc.) save you more than than you’re paying for? Then it’s worth it to buy the plugin so you can spend your time on things you specialize in.
Rob