This code is so valuable I doubt anyone will just opensource it. And it's far from easy to write, as someone said there is probably only a handful working ones out there.
The same could be said about bruteforce code. Many years there was only crappy and slow LBC, then I payed a rather modest $450 to freelancer to fund opensource vanitygen fork.
In the same time Bitcrack was already done and also opensource, just not popular.
In result, as I can see, author of Bitcrack was donated several times with 0.1 BTC. That's better than nothing (a doubt he could use same resources as zielar)