motto is definitely one of JAM's best songs and the only track by JAM I actually seek out and listen to amongst YUKI's solo works. the video is AWESOME and it was shot live (the sound source was done live in one take, so it differs from the actual studio recording) which is pretty awesome too.
JAM just went their separate ways peacefully more or less. YUKI started to do some random side projects in late 90's and early 00's with Mean Machine, NiNa, and Chara, and then less than a year after Judy and Mary's last album and final tour she released her first solo single and album and has been solo ever since. She also has been pretty adamant about not performing any JAM material and they haven't really made any statements as a group or done any sort of appearances together, so you could theorize there might be some bad blood, but since the group was started by YUKI and the bassist originally, I think it just time, they just wanted to work on other projects.
edit: this is pretty effing awesome