What commit are you on? (if you don’t know)
If you just cloned it recently (because this is your first time getting it started), you’re probably using the most recent commit.
If so, try this:
cd /usr/local/games/minecraft
npm install pam-authentication
This should install the PAM auth module that FreeBSD can alternatively use to get past the auth part.
Also, what version of FreeBSD are you using (uname -a)?
I’ve never heard of bhyve; I’ll see if there’s anything going on with this distro that might be causing conflict.