What is the ruling on money earned from work that led to missing congregational prayer, whether for the employer or the employee?

The fee taken for printing is lawful, and the abandonment of congregational prayer has no bearing on its prohibition. If your brother abandons prayer because of this, the fee does not become unlawful. Rather, he is sinful if he abandons prayer or performs it outside its prescribed time. However, if he prays on time but without a congregation, the matter is subject to scholarly disagreement, and the fatwa (definition) according to us is that he incurs sin.