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.
|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.|