Official clarification on the ToS:
https://twitter.com/HeroForgeMinis/status/1315837441756995594

(Transcription not available rn, apologies.)

Please boost this if you boosted the original post.

@starseeker TLDR for people with screen readers: They don't magically get the right to a character because you create it on their site, but they have the right to the assets they've made for their site, and you give them a license to what is essentially a combination of their assets, how you've configured and painted them, and other information you enter on their site, so they can provide things like the share functionality.