As you've guessed you're not allowed to sell anything you make with the free version. Apart from that there are no differences (apart from some advertisements in the default IDE; those are messed up and appear for me every now and then even though I have the paid version however...).
I don't see any reason why you wouldn't be able to build something using the free version, then purchase the license once you have something you want to distribute. Still so the license fee is very low and I'd say it's worth the price to have it for any eventualities.
"Why do programmers get Halloween and Christmas mixed up?" Because Oct(31) = Dec(25)