Box Billing

Has anyone tried Box Billing client managment and billing script? I'm considering using it for my web design company. I have tried it before but that was probably a couple of years ago. 

• Can you edit the code and use hooks?
  
• Can you style it to match of your website style?
  
• Are most payment gateways supported.?
  
• How secure is it?
  

Thanks in advance for any feedback. Here is the url if you have never heard of it before: http://www.boxbilling.com/

Theres a free version and a pro version. You can also install via Gigarank control panel (Softaculous)