A few days ago a buddy of mine asked how to get his CFBuilder 2 serial number. Turns out you can't do that from the IDE itself. I reached out to the engineers and Krishna shared the following tips with me:

Option 1) Register the product using Adobe ID (Help->Register Adobe ColdFusion Builder...). After sometime, it will be updated in Adobe license database and can be retrieved from

https://www.adobe.com/account.html

Then click on My products by authenticating with Adobe ID. You can see your product serial there. This option is only for Retail serial keys.

Option 2) Contact support.

Probably a good idea to copy down all serials anyway. I use Evernote for stuff like this.