New typescript version of superformulas - license concern

[jfstephe]

Hi,
I've moved superformulas to v4 (locally) and would like to create a Typescript version too. I'm happy to create a PR into the new plugins area but I'm not clear on the license.

Presumably I should copy the license.txt from this repo, but at https://bl.ocks.org/mbostock/1020902 this seems to use GPLv3, which I don't want to/cannot use in my codebase as I'm working on a commercial app.

As the owner of both sites can you clarify this position?

Thanks,
John