Hi,

I built a small add-on module for WHMCS that works with the linode api. So that if you have customers. You can easily give them dns zone access. (If you decide to not run DNS on your linode)

It's open source available on github.
https://github.com/srpurdy/WHMCS-Linode-DNS-Addon

Some of the features for admins include:
Opt-In Servers (So you have more than 1 server you can choose which will use this addon)
Link Existing Customer Domains to Zones
Give or Revoke Access to a DNS Zone
DNS Skeleton per server. (You can configure default Zone records that will be created when a customer adds a zone or orders hosting services)

Client Side Features
View DNS Zones (Access required)
Add New Zones
Edit Existing Zones
Add Records
Edit Records
Delete Records

Hope someone finds it useful. I do