Because they did it for their own personal use, and then published the source code under a BSD license for people to do with it whatever they want. Including porting it to other platforms.
But you know what, when you face a thinking wall like Elysia, you can either ram through it like in the good old days, or just ignore it and go around. The first will only get me banned in this politically correct internet. So the second option is better. It comes at some cost, because I do have to swallow the anger that comes from realizing I never learn and once again engaged with perhaps one of the most ignorant and stupid person I have ever met in 25 years of online presence. But I am not ready *yet* to be banned from cboard.