I had spent a little bit of time to get this one to work, but here it goes
OS - FreeBSD 4.10 p3 with linux compat installed
I was unable to use any command line command to create the password, however after stumbling over this document, I was able to get the perl script and everything works now... good luck
http://bazza.com/code/mkpass.html
copy the source to mkpass, chmod +x it to make it executable
bsdmulticast# ./mkpass
Enter password: nobozos
Encrypted pass: nopb3xWGYit02
add the text into the proper place in vls.cfg, restart the server and enjoy, this assumes that you have the perl port installed...