When I was having to code on my Thinkpad I downloaded my mode file for jEdit from here and realized it wasn't my lastest version as some of the syntax highlighting wasn't the same as on my iMac. I got my iMac back, so here's the current version.

To use the syntax highlighting, put the assembly-6502.xml file in the MODES directory of jEdit. Then edit the catalog file in the same directory and add the following.

<MODE NAME="assembly-6502"  FILE="assembly-6502.xml"
                            FILE_NAME_GLOB="*.asm">

I had to disable the assembly-x86 as it also uses *.asm for the file extension. I disabled it by changing its entry as follows(removed the *)

<MODE NAME="assembly-x86"   FILE="assembly-x86.xml"
                            FILE_NAME_GLOB=".asm" />

assembly_6502.xml.zip