Is it permissible to work on developing a vehicle tracking system for another company, and what is the ruling on that in terms of betrayal or treachery to the current company, knowing that the other company may be a competitor, and that the current company has not paid salaries for 6 months?

There is no harm in working with the new company as long as you do not disclose the secrets of the first company, and your work is outside of its official hours. However, it is not permissible to work with the new company until one year has passed since leaving the first company, due to the condition of not working for a competitor. The first company's delay in paying salaries does not permit violating this condition; rather, it allows you to annul the contract due to harm, in accordance with the hadith: "There should be no harm nor reciprocating harm." Thus, any excuse that makes it impossible to fulfill the contracted obligation except by harm to yourself or your property grants you the right to annul the contract.