Coldfusion 9 license migration

Sea6, only Adobe can speak authoritatively of course. But I'd think the answer would be "it depends". 

First, we should clarify that each version of CF has its own EULA (End User Licensing Agreement), and you are asking about CF9.

Second, you refer to moving CF9 to the new server and running them "side by side", but would production traffic really be going to both at the same time? If not, then perhaps technically the one that is "not" running would be considered used for "backup and disaster recovery". You can read the terms here (the CF9 EULA, recovered via the archive.org site):

https://web.archive.org/web/20111112023951/http://www.adobe.com/products/eulas/pdfs/adobe_coldFusion_combined_20090811_0930.pdf

(BTW, this is NOT to be confused with the first result that comes up (for me) in Google search for:coldfusion 9 eula

https://labs.adobe.com/technologies/eula/coldfusion9.html

That one only refers to CF in the title of the page, but nowhere else, nor does it refer to other words that have always been in CF EULA's, like production, developer edition, etc. I think it's some mistaken page (note also that it's on the "labs.adobe.com" site), but it's a shame it comes up first.)

And if you want to read more about the changes to the EULA that were introduced in CF9 specifically, see these posts by then-Adobe employee Terry Ryan:

http://terrenceryan.com/blog/index.php/coldfusion-9-eula-changes/

http://terrenceryan.com/blog/index.php/coldfusion-9-testing-staging-and-development-changes-to-eula/

Of course, CF9 is no longer supported (nor is CF10), so you'll find it harder and harder to get any answers about those, but perhaps the resources above will help you make a determination of what's best for your org. Or, of course, see a lawyer (and see comments in the posts about some who STILL expressed concerns about risk of BSA audits.)