Is it permissible to sell a computer program belonging to a company for the purpose of collecting unpaid financial dues after resignation, knowing that the selling price is equivalent to the value of the dues and that the sale will take place in a location where the company does not operate?

If you are unable to obtain your legally established right through judicial means, it is permissible for you to take the equivalent of your right without exceeding it. This is known as the issue of al-Zafar (taking one's right by force/stealth). The majority of jurists have agreed on its permissibility, citing as evidence the hadith of Hind bint Utbah and the hadith of the guest, where the Prophet, peace and blessings be upon him, permitted taking one's right from someone who refused to fulfill it. The conditions for the permissibility of al-Zafar are: that you do not take more than your right, that you are safe from scandal and punishment, and that you are unable to access your right through judicial means.