This is not a module, which adds feature for your users,
but will increase the number of interfaces other modules could use to interact with your vtigerCRM.
The module itself don't slow down the performance.
You found the Setup Instructions and Download here:
https://github.com/swarnat/vtigerCRM-EventHandler/tree/master
You found the Setup Instructions and Download here:
https://github.com/swarnat/vtigerCRM-EventHandler/tree/vtiger6