Now I'm injecting my own opinion here but I always saw AHG as a way for Boy Scout leaders who knew the BSA system and saw GSUSA as foreign (lack of chartering organizations, outdoor program, etc.) to create an alternative program that was also more religiously conservative. Also since BSA and GSUSA don't usually play nicely. This partnership allowed BSA COs to have a parallel program for girls under their organization that would allow families to find a program to accommodate their sons and daughters.
However AHG got its start by mooching off the BSA. Its YPT was the BSA YPT with amendments and rather than develop an advanced volunteer leadership course they sent their leaders to Wood Badge.
Can AHG stand on its own with out the BSA?