What is the mechanism for calculating each partner's share upon separation from a project that was equally funded, and its profits expanded due to their support over 3 years, with one of the partners wishing to acquire the project?

The share of each partner is calculated based on their agreement. If each partner contributed half the capital and they agreed to divide the profits equally, then each owns half of the company. If one partner wishes to sell their share to the other, the company's assets must be inventoried, its debts settled, and its rights collected. Then, the value of the company's assets is calculated, and each partner is entitled to half of that.

If the company can be divided, it should be divided between them. If they agree that one should buy the share of the other, there is no harm in that. However, if they disagree and the company cannot be divided, and each wishes to buy the other's share, the one who refuses cannot be compelled to sell, because consent is a condition for such transactions.