Is it forbidden to acquire discounted goods using automated programs, given a condition that stipulates against the use of external programs? And what are the consequences of violating this condition?

You must adhere to the site's condition for obtaining the discounted item by not using any program or exploiting any loophole. Violating this is forbidden due to the Prophet's (peace be upon him) saying: "Muslims are bound by their conditions." There is no excuse for the violator due to the large number of those who do it. As for someone who took it this way out of ignorance, there is no sin upon him, as Sheikh al-Islam Ibn Taymiyyah said: "What was taken by interpretation or ignorance, then for him is what has passed, without a doubt." As for what was taken after knowing, it must be returned to the site if possible.