I've fixed the busybox issue, looks like in ESXi 5.1, all the utilities are automatically symlink, so that's why busybox itself is not in the default path. You can check out the fix in the development branch https://github.com/lamw/ghettoVCB/commit/5bbf40bb3297cd39b53e4ad3b6931b9a7a26f31f
I also tested the cronjob on ESXi 5.1 and for the same reason as above, you no longer need to call "busybox crond", you can just do crond.
So the process for ESXi 5.1 (I will update the documentation) is as follows:
1) Create your cron entry
2) Kill the existing crond by running:
kill $(cat /var/run/crond.pid)
3) Startup crond by running:
crond
4) Verify crond started by running:
and you should see something likeps | grep crond | grep -v grep
202665 202665 crond crond