I will probably not bother with this minor issue, since:
- It doesn't change anything to the way the viewer works.
- The (stupid) future allowance for teens in SL might well make LL change again "General" for "PG" one day or another (especially if/when they allow 15- teens on the grid).
- Some OpenSim grids do use PG and Mature for their actual meaning (and the Cool VL Viewer is not exclusively for use with SL).