Bases loaded ball hits runner....
 

Bases loaded, nobody out, and the batted ball hits the runner advancing to 2nd. I understand that the runner is out and it's a dead ball, but do all of the other baserunners go back to original base or does the forces runners get to advance and a run score?

This is a form of interference. In USA Softball, all runners return to the base last occupied at the time of interference.

In your play, the runners who started on second and third would return, assuming they have not touched home and third respectively. The runner from first is out, and the batter is placed on first.

All runners return to last base they occupied at time of interference. No runs score and batter runner placed on first. One out bases loaded. Never reward the offending team.

This was high school softball. I thought that was the rule but wanted to make sure

NFHS and USA Softball are the same for this rule.

Unless, of course, that batted ball had already passed the fielder and no other fielder had a chance to make a play, in which case it's live ball, play on...