SSMS is now a completely standalone product, not tied to any specific version or edition of SQL Server, and no longer requires licensing of any kind. You should also note that there is a new, much more aggressive support policy, meaning you will want to stay up to date. If you contact Microsoft about an issue with a build that is even a point release behind, they will likely just tell you to upgrade.
You can always download the latest releases of SSMS here. Typically, you should expect a new build about every 30 days, though – as you can see below – they will sometimes take a little longer, or even sneak in an out-of-band release. To me this is way better overall than the old model, where sometimes we would wait months or years for any change at all.
Finally, if you're looking for Azure Data Studio, the latest version can be downloaded here, and the release notes are here. However, starting with SSMS 18.7, Azure Data Studio is now installed with SSMS.
|18.0 Preview 7||15.0.18092.0||2019-03-01|
|18.0 Preview 6||15.0.18075.0||2018-12-18|
|18.0 Preview 5||15.0.18068.0||2018-11-15|
|18.0 Preview 4||15.0.18040.0||2018-09-24|
|SQL Server 2014 (SP1)||12.0.4100.1||2015-05-14||Download|
|SQL Server 2012 (SP3)||11.0.6020.0||2015-11-21||Download|
|SQL Server 2008 R2 (SP2)||10.50.4000||2012-07-02||Download|
|The 2008 R2 link takes you to the 2008 R2 Express download page. When you click "Download" on that page, you'll have some choices; for SSMS you want SQLManagementStudio_x64_ENU.exe or, if your hardware is from last century, SQLManagementStudio_x86_ENU.exe.|