We've updated the FAQ article on ethical cloning of FontStructions.
If you do publish a clone with small changes, please give it a distrinct name, to avoid confusion with the original.
Please also indicate what changes you have made in the FontStruction description field.
It’s difficult to make “rules” on these things – it’s just a matter of being respectful to the original designer, who is kind enough to permit the clone.
Unethical cloning has negative consequences for the community as it discourages designers from sharing their work.