Zoph is Free Software. Although the word 'free' here stands for freedom and not for gratis, in the end, that is what you pay for Zoph: nothing! But, the fact that it is open source software, gives you more advantages than just an infinite low price. For example, if I ever decide to stop working on Zoph, someone else can take over. Also, if you want to make changes to Zoph, you are free to do so at your wish, you may even give away your changed version, as long as you continue to publish it under the licence that makes all of this possible: the GPL.