This is where international law applies. It depends on where iBaker lives and if he is subject to the laws of France.
But again... It was agreed upon and in even in Waindigo own words, that he has not completed the product and is demanding more money and if he doesn't get that money... He will release it publicly under new terms.... ie... Extortion. You're copyright argument is invalid as iBaker paid for the code and the finished product, which has not yet been delivered.
And while under France law Waindigo maybe able to release the product with further features.... The original requested features would still be under the original agreed upon payment. So if Waindigo released version 1 today and it took until version 8 for all those features to finally be made public... iBaker would be entitled to version 1 through 8 under the original payment.