It is possible, I have done it before on my sister's iPad, the passcode is stored in a plist file in the iPad backup.
I will return when I find what the plist file is called.
Also note that synchronising with a computer will create a backup on your computer.
So I have looked it up, this appears to only work in iOS 4. I see a possible way around it in iOS 5 but I have not tested this new method.
Find your backup folder. Windows:
%AppData%\Roaming\Apple Computer\MobileSync\Backup\ and Mac:
<your home folder>/Library/Application Support/MobileSync/Backup/
Open your iPad's backup - this involves a little guesswork (if you sync more than one device). However, you can check the date of the backup in itunes preferences, then find the backup in the folder with the same date.
If you are using iOS 5 here - see if you have an iOS 4 backup with the passcode. If you have an iOS 5 backup only backup your backup. I have not tested the following method.
Locate the file
662bc19b13aecef58a7e855d0316e4cf61e2642b (no extension). Open with a Property-List (plist) editor - link from Youtube. (Mac comes with a built-in one).
Look for the key
SBParentalControlsPIN. Underneath is the 4 digits of the Restrictions Passcode. If you have an iOS 5 backup, you won't find the key and you need to do step 6 instead.
WARNING! THIS MIGHT BREAK THE BACKUP, BACKUP YOUR BACKUP FIRST. I HAVE NOT TRIED THIS, I CANNOT VOUCH FOR IT WORKING: - Locate the key called
SBParentalControlsEnabled. Uncheck the box, or change from
false, or similar. Restore your iPad from this backup. IF IT FAILS, REPLACE THE MODIFIED BACKUP WITH THE ORIGINAL COPY THAT YOU MADE, THIS WILL GET YOUR STUFF BACK.
Hope this helps, and sorry if it doesn't.