That photo was for the cameras, the two were messing around. Luke was with them also.
Shannen said in Radar that if she wasn't saying what happened between her and Jason because it was no ones business. But she wasn't
really hinting at anything.
Every website has quoted that bit of the magazine. I remember her saying in an interview that her and Jason had flirted and hung out lots, that they were great friends but one of them was always in a relationship so it never led to anything.
*hugs*
xoxoxo