The following tutorial is just a more step-by-step version of Multiple guest users on one PC - How to register Starry Night, and with Munki in mind.
Find the Starry Night app in your /Applications folder, right-click it, and select Show Package Contents.
Then, go to Contents > Resources > Sky Data > Resources and find the p.ssd file.
Open up the p.ssd file with a text editor. I'd highly recommend a custom text editor like TextWrangler instead of Mac OS X's built-in TextEdit.
At the bottom of the text file, paste in the following two lines:
<SN_VALUE name="LicenseeName" value="Username">
<SN_VALUE name="LicenseNumber" value="Registration Number">
and replace Username
with your actual licensed username and Registration Number
with your actual licensed registration number.
Then save and close the file.
Go ahead and do a munkiimport on the Starry Night app. The developer is Simulation Curriculum Corp.