What is the ruling of Islamic law on programming and publishing a computer program for calculating the numerological value of letters (Hisab al-Jummal), knowing that sorcerers may use it?

There is no harm in creating and publishing programs that are permissible in themselves, even if they might be used for something forbidden. This is because most permissible things are like that. However, if a person knows that a specific individual will use the program for something forbidden, then it is not permissible to give it to them.