Bittersweet to find this forum post.
I've had BFD since v2 came out and have had to reinstall 3-4 times since buying a BFD3 upgrade and moving onto newer workstations over the years. Other than the first install, 100% of subsequent ones have been a major PITA.
So here I learn after banging my head on a Sierra install attempt with anti-virus, firewalls and vpn turned off in an admin account that it's "normal" for us to have hosed installs; intermittently since October 2016. You'd think if a developer slacked off on their installers they'd at least put workaround caveats in their install docs rather than send customers on a hunt through support forums.
After one more attempt at solving this issue, I'll begin trying to figure out why any packs I ever bought (two at most) no longer show up in my downloads. Hurting for sales these days folks?
If this terminal procedure doesn't work for install, my longstanding relationship with FXSpansion will also be, well - terminal.