It works fine in GBS 2.0 - the author is just saying it's not written for more than 9 actors. I was able to bump it up to 14 by starting the variable count at 80 and modifying the "ParentedActors.c" file with this code:
void PositionParentedActors() {
UBYTE j;
// Linked sprite magic
for (UBYTE i = 1; i < 15; ++i) // loop through the control variables
{
UBYTE parent = script_variables[i+80] & 0x0F;
UBYTE L = script_variables[i+80] & 0x10;
UBYTE U = script_variables[i+80] & 0x20;
UBYTE D = script_variables[i+80] & 0x40;
UBYTE R = script_variables[i+80] & 0x80;
// set position relative to player
if (parent == 15) {