Thanks to all of the answers, but I think I found what I was looking for in the Visual Studio Community Edition license: https://visualstudio.microsoft.com/license-terms/mlt031819/

My understanding, is that this allows me to use Visual Studio 2019 Community Edition for SSDT tools in an enterprise setting.

You don't have to install SSDT in Visual Studio 2019, even in Community. Go to new project and type SQL and hit return. It will say something like "SQL Server Database Project". Guess what? That's SSDT. In older versions, it was a separate install. It is now part of the core Visual Studio. And you upgrade it, if there are any, the same way you do anything else.

Already installed Visual Studio? No problem. Reopen the installer and install the data tools. This can be part of the payloads they have (I forget which one, but it has to do with data) or you can click on the tab that allows you to install individual components and search for the SQL tools. Once installed, they are there.

I don't belie you can install using the SSDT separate installer anymore, just like you know handle all of the .NET Core installs in Visual Studio, rather than separate. Kathleen Dollard outlined this in one of her posts last year (not SSDT, but .NET Core, etc.), so it has been a bit more than a year these things got folded into the installer. Core may still allow download and install? Not sure. But SSDT is the SQL project in 2019.

I guess that you can use SSDT anywhere where you can use Visual Studio. In other words, if you can use Visual Studio - you can use SSDT as well. Now the question - can you use Visual Studio? Here is the link to pdf document describing their Licensing policy. Here is the snapshot from there:

Visual Studio Community 2019 is a free, full-featured IDE for any developer building non-enterprise apps across any platform or device. It includes all the capabilities needed to create compelling non-enterprise applications, including powerful productivity features, mobile development tools for Windows, iOS and Android, and access to thousands of extensions.

Who can use the Software

Rights to use Visual Studio Community depend on the customer segment and usage scenarios as explained below.

Individual developers

Any individual developer can use Visual Studio Community to create their own free or paid apps. In addition, any number of users may use the software to develop and test device drivers for the Windows operating system.

Organizations

• An unlimited number of users within an organization can use Visual Studio Community for the following scenarios: in a classroom learning environment, for academic research, or for contributing to open source projects.

• Any number of users may use the software to develop and test device drivers for the Windows operating system.

•For all other usage scenarios: In non-enterprise organizations up to 5 users can use Visual Studio Community. In enterprise organizations (meaning those with >250 PCs or > $1M in annual revenue) no use is permitted for employees as well as contractors beyond the open source, academic research and classroom learning environment scenarios described above

VS Code - is the text/development editor that have nothing for SSDT, you can work with SSDT projects like with files and folders. You won't be able to build/validate/deploy the project.

ADS - the text/development editor that was created on the base of VS Code to work with SQL Server databases. You can do some basic stuff for SSDT projects (build, deploy, compare, add/remove objects), but is not so powerful as Studio SSDT version yet.

Technically you need only MSBuild and SQLPackage to build and deploy dacpacs, so if these tools can be used for free in Enterprise, then you can technically do everything without the Studio, just with ADS or in hard-core way - with any editor if your knowledge is deep enough to generate proper sqlproj (xml) file.