Hashicorp have Terraform registered as a trademark[0] and they themselves have said they don't want the name used in a way that is confusing or suggests enforcement by Hashicorp[1]. So the GP definitely cannot call themselves "OpenTerraform".

[0] https://tmsearch.uspto.gov/bin/showfield?f=doc&state=4810:yj...

[1] https://www.hashicorp.com/brand

Cosmoform, NexaForm, UltraForm, TerraCraft, PlanetaryForm, TerraNova, TerraMatrix, TerraBeyond, SpaceMold, AstroForm.

Pick your favorite.

So, earthform? :)