Doubt about how many licenses I need ColdFusion STD 2018

Your answers will be found in the ColdFusion End User Licensing Agreement, which is available online or within any installation of CF. (I did a blog post on finding it.)

And the answer may not be as easy as some may assert it to be. Of course, there is the free Developer edition, meant for local development. But you're talking about a "dev" server, where developers (and perhaps others) would access it, right? The Eula distinguishes those. One is the "developer edition" and the other is "development software".

There have been changes over the years regarding use of a production license on a development server. In CF9, it was simply that yes, you could take a production CF license and use it on a development (or even staging) server.

But that's been refined in the releases since then (10, 11, 2016, and 2018), and it now precludes that Dev server being accessible by folks outside of your internal network. From Section 1.8 of the 2018 EULA:

"Development Software” means Software licensed solely for (a) internal development and testing; and (b) for use on a Staging Server, when Licensee is using the Software with respect to a valid license to the Production Software. In each case the Development Software may only be accessed by Authorized Users over the Licensee’s Internal Network."

And there is more in its section 3.2 on this development use.

So bottom line: one should read the EULA to know things for sure. It's only a few pages, and only a few key paragraphs apply here (though it's legalese, so a bit obtuse). It could be that you don't need a separate license for your development server, or you may, depending on those clauses.

Finally, you can always call Adobe sales to ask them, though that has proven difficult for many, since it's a large org and it may depend on who you reach, as well as how well they will know things like even these CF EULA terms, how often they are asked, and whether they would reflect it accurately.

But you can also reach out to an Adobe reseller, especially on who focuses on CF and such may get such questions often. An example is Intergral, makers of the FusionReactor monitor for CF, who have a CF reseller site at https://buy-adobe-software.com. They offer an email and phone number on the top right of the site, and you will speak to someone knowledgable, who could clarify things for you (again hopefully in line with even such subtleties of the EULA on this dev server question).

Hope that helps, you and future readers.