What is the ruling on working as a programmer for a foreign company if part of the work involves writing software for a liquor company?

It is not permissible to complete work for a liquor company after becoming aware of the true nature of the situation, as this constitutes aiding in sin. Allah Almighty says: "And do not cooperate in sin and aggression." As for what was taken as wages before knowing of its impermissibility, it is lawful. However, what is taken after that is unlawful and must be given away in charity.