When 2 plugins have the same dependency

Outcome when modifying constructor of license manager included in Dummy Plugin One:

string 'Hi from "/vagrant/www/public/wp-content/plugins/dummy-plugin-one/vendor/yoast/license-manager"' (length=94)
string 'Hi from "/vagrant/www/public/wp-content/plugins/dummy-plugin-one/vendor/yoast/license-manager"' (length=94)

Meaning that the second time the license manager is included, by Dummy Plugin Two, it is ignored by Composer.

Test this yourself

Clone repository and run composer install in both plugin directories. Modify constructor in dummy-plugin-one/vendor/yoast/license-manager/class-plugin-license-manager.php to include:

var_dump('Hello from ' . __DIR__);