Standard MagCast licenses are non-transferrable as outlined in the terms here: http://magcasting.co/terms.php which means that empty MagCast licenses can not be sold or transferred.
However an already published MagCast can be sold.
The way this process works is that the buyer will need to take control of both your MagCast and iTunes Connect accounts after the sale has been completed.
The buyer can then update his contact email with MagCast Support and continue operation of the MagCast as per normal.
That is the simplest way to transfer ownership.
NB! If you own bundle licenses, these specific licenses can be sold and allocated to an account of your buyers choice.