There are sure really funky tos that make it sound not free and that they own anything you create but I didn't have to pay to use it. Not sure if it watermarks anything you export because I haven't made anything that doesn't look like my 2 year old made it.
Yeah, the website didn't give me the impression there was a free version. Everyone should keep in mind, though, that whatever you create for "free" is owned by Inkarnate, according to their policies. You are not free to use those maps you make for anything but personal use without permission from Inkarnate or a license from them. So that prohibits the use of their maps in any content you might make that you would share with the community.