Only if a plusless user has the MP3 already. If you don't have the specified plus-only music file, it doesn't crash. If vanilla players don't bother downloading plus, I'd doubt they'd know how or bother with downloading music files either. And no, plusless users cannot download music from JJ2 servers.

Many of the LK avalon players who only have this version cannot speak english at all, only Polish. Most plusless players are stuck in the language barrier or don't chat at all, or simply don't see plus worth it, or they won't bother figuring out or won't bother downloading a real version of JJ2. Therefore they are very disconnected from the actual part of the JJ2 community.

To be honest, I couldn't give a care less for these kind of players anymore. Not only are they terribly skilled players (the majority just walk, stand and shoot idlers), but they haven't contributed anything. Even many plusless players (yes, some had a compatible version, but some refused to tell me what version of JJ2 they had) who do understand English, whenever I told them about plus and how to get/install it, they were very ignorant or reluctant. 9 times out of 10.