That's strange, if you're denied read access to the iPhoto directory then I'm wondering how you can see the image in the first place....
Anyway the easiest non-destructive way to accomplish what you want to do is to click and drag the photo(s) you'd like to upload to Photobucket to the Desktop. (You'll know if you are making a copy of the pictures when the green plus "+" icon shows up under the cursor.) Simply upload the pictures on your desktop and then delete them when done.