[FabHK]

The point stands, though - NR gives a nice introduction, and allows you to dabble with code and algorithm. But the NR code is didactic, it is not production quality (nor is it intended as such). Together with the restrictive license terms, that means:

For anything to be used in the real world, in production, you're better off taking code from somewhere else.

What alternative to use depends on the topic/algorithm in question. But NR should just be a starting point, not what you actually use.