If the program is a derived work of both the GPLed source code and the
CC-BY-SAed language files, the resulting work has already been
non-distributable before because the two licenses are incompatible. The
new NC clause and the vague statements on the website only add insult to
injury.

You should contact Jlatexmath upstream to check whether they gave an
exemption to geogebra. If not, they might want to apply some pressure.

Hendrik