Donating to KiCad via The Linux Foundation is the preferred method of supporting KiCad development. This support provides funds for project development and the developers behind it. The Linux Foundation is a 501(c)(6) non-profit organization in the US.
Donate via TLFCERN is a long time supporter of KiCad. Donating money via CERN will pay KiCad developers for software development. Your country's tax laws may provide you with a benefit for this donation.
Donate via CERN