Does the Hadith: "He who deceives us is not of us" apply to a government employee who designs and sells programs in his spare time, knowing that the law only permits government employees to hold one job?

A salaried employee is considered a special employee if his contract is for a fixed term. In this case, he is not permitted to use his time allocated for work for anything other than the benefit of the employer, even if no work has been assigned to him, unless with explicit or customary permission from the employer. If custom permits it, then there is no harm in him utilizing his free time in a way that benefits him and does not harm the employer. However, if the employer prohibits it, the employee is not allowed to do so, even if many others violate the rule, because Allah Almighty says: ﴿O YOU WHO HAVE BELIEVED, FULFILL [ALL] CONTRACTS.﴾

As for working after official working hours, the general rule is permissibility, unless the contract stipulates otherwise, in which case it is obligatory to adhere to it, based on the saying of the Prophet, peace and blessings be upon him: "Muslims are bound by their stipulations."