First, create a group on the Open/Active Directory Master containing the users who should have local admin rights. Then, add this group to the local admin group. Example: For the Open/Active Directory group sysops, issue the command

dseditgroup -o edit -n /Local/Default -a sysops -t group admin

as root. To add the user larry, the command would be

dseditgroup -o edit -n /Local/Default -a larry -t user admin