Gun,
You can do anything you want with the code because I released it for free, but don't say to your customers that you have developed from zero like @Sweeet said. And cite the developer when you copy something from someone that spent nights developing this thing. This is how open-source works.
Hey, Rafael! Just to be fair, ~Gunthar doesn't tried to hide or fabricate any data, nor have said anywhere that he is the sole creator of the bot. Moreover appropriate credits are listed and you and Paulo Alexandre are mentioned in package.json as long as your bot is used as a wrapper.
And in addition to trading stragegy tuning ~Gunthar offered an excellent level of customer support as well as pretty comfortable interface to run the bot for Windows users and, what most important, he is unstoppable in development and bug fixing.