MySQL (OPTIONAL)
(NOTE: If you're using this test framework from a local development machine and don't plan on writing to a MySQL DB from your local test runs, you can skip this step.)
Mac:
brew install MySQL
Windows: Download MySQL here
That installs the MySQL library so that you can use db commands in your code. To make that useful, you'll want to have a MySQL DB that you can connect to. You'll also want to use the testcaserepository.sql file from the seleniumbase/core folder to add the necessary tables.
If you want a visual tool to help make your MySQL life easier, try MySQL Workbench.