Extension licence

I am thinking to buy some extensions .The problem is i have some 2 - 3 site . Can i use the same extension on all my sites ? or i have to purchase seperatly ?

Bumop

bump ?

You can only use one license per web site. It's as simple as that. Or are you talking about modifications? Because, I thought you were talking about licenses.

If you are referring to modifications, then that's up to the developer.