How many licenses of coldfusion enterprise do I have to buy?

With all due respect, Rahul, this question doesn't seem to warrant needing to be "passed to a licensing expert". It just requires a careful reading of the End User Licensing Agreement for CF2016 .

At least for the question John has posed, the answer seems pretty clear (as I will relate below). Of course, there are certainly other matters discussed in that EULA that DO require an Adobe licensing expert or lawyer to parse. :-)

So John, as I read it, no, you don't need to "buy 2 licenses" in the scenario you describe. You have either of 2 choices, both not requiring a purchase of a license for development (the first applies to anyone, the second applies only to those who DO buy a production license, whether Standard or Enterprise, who want to use that license for a testing server, with a slight variation for each edition).

First, let's make clear that if you were simply to implement the "developer edition" of CF on the dev server, that's clearly free for development. Just install CF, and choose the "developer" edition in the opening prompts. Something to note is that this developer edition will be limited to accepting requests from two IP addresses at a time (and of course is not intended for production or other than development use). See sections 1.7 and 3.3ff for more on the Developer edition.

But second, if you need to lift that "2 concurrent ip" limitation for your use of CF on a development machine, the EULA clearly indicates that "For each Enterprise License of Software, obtained by Licensee pursuant to Section 3.1.1, Licensee gets the right to install and use the Software as Development Software." So that covers you, having purchased an Enterprise license.

And for anyone using CF 2016 Standard, it goes on to say, "If Licensee has obtained more than one license for Standard version of Software under section 3.1.2, Licensee may use one of such license as Development Software.". So that seems to indicate that one has to have bought at least 2 CF 2016 Standard licenses to use one of them for a development machine.

For more on this second point about using a production license for "development" (as opposed to the "Developer edition"), see also sections 1.8, 3.1.3, 3.2, 3.2.1, and 3.2.2.

If anyone (from Adobe or otherwise) feels that I have somehow misread or misrepresented things, let me know.