Looking at Ngspice's upstream source code shows that only the Ngspice's User Manual (and documentation) falls under the "SPICEDOC" license. Curt may be able to assist with changing its license as well, otherwise Debian could distribute it separately from Ngspice itself. I am not sure what specific project caused Ngspice to inherit this documentation license.
It seems the animation and differentiation routines for xgraph written by Paul Walker at UIUC is licensed with the ownership of modifications restriction and non-commercial clause. For this piece of Ngspice we would need to contact UIUC.
As for the unspecified works, I'm not sure what should be done, maybe the FSF could advise.
For now, I believe we should focus on changing CIDER1b1's license since it is a low hanging fruit and is very critical to Ngspice's simulations, then we can move on to the rest.
How should Curt go about making CIDER1b1's license change?