What is the ruling on using a dictionary program that contains several dictionaries to search for the meanings of unknown English terms, given that one is not certain whether its designers acquired the dictionaries through contracts or not?

It is permissible to use a dictionary program to search for meanings of terms, and the user's lack of knowledge regarding the lawfulness of how the program owners acquired it does not affect this, for the default is permissibility. Sheikh al-Islam Ibn Taymiyyah clarified that the unknown is like the non-existent, and the default assumption for what is in a Muslim's possession is that it is his property. If a person is ignorant of the status of property in someone else's possession, the matter is based on the default assumption.