Adobe staff does not officially monitor these forums. These forums are for user-to-user support. You need to email Adobe directly to ask about your licensing question.
It's my understanding that a license can only be installed once on any given network. If you have a network that is isolated from the internet and the other network that has the licensed version, you could probably get away with it.
You can install a developer version (choose "Developer Edition" during install, do not provide a license key) without any issue. It's just as robust and feature-rich as a licensed version; the only difference is PDFs created by CF will have a watermark on them indicating that a developer version of CF created it.
Thanks for the info regarding Adobe staff, I don't suppose you know what the official Adobe support email address is?
The license agreement suggests that the production license can be used for development software, clause 3.2.1:
For each license of Production Software, obtained by licensee, Adobe grants Licensee a license to install and use the Software as Development Software on one Server... strictly for testing, development, and staging purposes, to be used and accessed by Authorized users over the Licensee's internal network.
The license agreement differentiates between development software (1.8) and developer edition software (1.7). The biggest limitation of the developer edition is only allowing 2 simultaneous IP addresses, which I also believe can only be changed by restarting the service. From reading the license agreement I'm fairly sure we can use the same license for testing I just need an official statement from Adobe and would like confirmation that the same serial number can be used for both installations.
I could be wrong, but it's my understanding that if two CF installs have the same license and are on the same network, it will raise a flag. I don't know if it will disable one or the other, but I believe it sends a notice to Adobe. That's why I suggested that if the test environment is isolated from the production environment, it shouldn't be a problem. And as far as Developer allowing only two IP addresses, it used to be one IP address. But do you need more than two IP addresses for testing??
Unfortunately, I do not have the email address for Adobe Licensing. I think the adobe.com website has email addresses listed for install support, licensing support, sales and billing support, et al.
I believe the End User License Agreement (EULA) for the most recent releases of ColdFusion (10, 11, and 2016) specifically permit the use of a single serial number for one production server as well as an additional testing/qa/staging server (as long as it's on a private network - not exposed to the internet. Here's a link to the EULA for ColdFusion 2016: http://wwwimages.adobe.com/content/dam/acom/en/legal/licenses-terms/pdf/ColdFusion-2016.pd f. Note section 3.2.1.
In the past, Adobe staff have confirmed that you simply enter the same serial number on the testing server.