United States copyright laws are very clear on this: As soon as you create a work, it is considered copyrighted and nobody can tell you what you're allowed to do with it.
In other words you have the legal right to sell anything you create no matter what software you used to create it with.
These types of work are protected under US copyright law
However, derivative works are a different story and you should think carefully before selling something you did not create entirely on your own.
Unless the author of a prior work gives you permission to copy, it's considered copyright infringement: