You should take the money if your pal insists. lol But then you will have to ask your pal for the permission to release the script, since he or she'll have the ownership. And as stated, you've written this script voluntarily for your pal without monetary exchange involved, you do whatever you want with it. And don't be surprise people modify it, (in a bad sense, rip it) chances are they will. This is what happen with open sourced codes these days.