Are you referring to the "...and one Front-Cover Text: ``Available free from http:openfoam.org[openfoam.org]''" part?
I'm afraid that this really means that freefoam-doc would have to move to unstable. I'm very sure upstream would not consider removing that sentence, as newer versions of the document are now even CC BY-NC-ND. -- To UNSUBSCRIBE, email to debian-bugs-dist-requ...@lists.debian.org with a subject of "unsubscribe". Trouble? Contact listmas...@lists.debian.org