BuddyPress.org

@rjhoward of course you’re free to develop in whatever platform is easier to tweak and mold to what you want. There are other options in the market – free and paid.

Related to create group problem above, when you can’t get default BP behavior working in your install, change to bp-default theme and deactivate all plugins except BuddyPress plus rename bp-custom.php and the mu-plugins folder.
Cheers.