Some people remove the link on every script they use, and when you hear the reason you will understand: When a security exploit in a script is discovered, bad people who would abuse that script go to Google and enter: "Powered by (script name)" which gives them a list of sites to attack.
Other than that, I can think of no reason to remove the link.
There have been many questions about this, and if it is allowed. I will offer you this link:
which should help.
All the best!