You can modify the GPL with an addition term that requires the use of green energy, but the resulting license is incompatible with the GPL with the result that code under the new license cannot be mixed with or linked with GPLed code. See section 7 ("additional terms") of the GPL:
https://www.gnu.org/licenses/gpl-3.0.en.html
(the GPL version 2 also has this property.)
Also, its unusual license is probably why jslint is not used much.