Are you using SPICE for the actual simulation?
> Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution.
unless you're violating the ngspice license? or the documentation and/or other materials are just hard to find?
parts of ngspice are also licensed under gplv2, cc-by-sa-4.0, lgpl-2.1+, or gpl2+, but maybe you aren't using those parts