Hi TCS,
I know nothing of any law suits against DownTube, frivolous or otherwise.
I do know that Tern will defend its IP where necessary.
And as far as i am concerned, I do not set myself up as a target for such an exchange on a forum.
By all means contact me directly about any concerns you have.
You know my contact details.
"mark . bickerton @ ternbicycles . com" (no spaces)
Mark