Is partnership and the profit generated from it permissible or forbidden, knowing that there is a clause in the contract prohibiting working outside the company, and that the partners are mutually agreeable and satisfied with this partnership?

The ruling on the parent company's stipulation that an employee should not work for another entity, whether directly or indirectly, depends on the company's purpose behind this condition. If the purpose is legitimate, then it is obligatory to fulfill it; otherwise, it is not. There is no harm in the money earned from the second job previously, as long as it was outside official working hours and did not affect the original work. However, for future work, it is preferable to seek permission from the parent company; otherwise, it is safer to refrain.