"Or from which store should one have lawfully purchased movies instead?"
^^^^^ That part of the fucking question right there. ^^^^^
There are other stores that sell music and movies legally. If you bought from Apple or anyone else something that's controlled by DRM your goods are subject to that DRM. If you bought someone else's DRM-encumbered stuff, it's not at all impacted by this. If you bought non-DRM stuff, it's not impacted by this. If you upgrade to a halfway recent OS, you're not impacted by this.
If you have the money to throw at a huge library of DRM-encumbered stuff, spend $80 on Windows 7 for goodness sake.
You can buy music places that let you listen to it without DRM. EMusic. Bandcamp. Megatunes. Oddly enough, FYE if you don't mind physical media.
Ummmm... Emusic isn't a player. It's a place other than iTunes to buy music. It comes as MP3 when you buy it.
I buy my movies and music from Google or every once in a while on physical media. It's pretty hard for Apple to screw those up.
Thank you for your correction. I'll post an apology for my English misuse on every light post in the area, from Seltjarnes to Mosfellsbær.
"Ninety percent of baseball is half mental." -- Yogi Berra