I've generally seen it been called white-hat. In my (limited) experience, black-hat is generally used to reference automatic link building, content spinning etc., while white-hat to reference link building through other means that Google will(or can) not automatically penalize.

black hat would be hacking websites and adding those links to he hacked websites. :)

No, black hat would be more comment backlink blasts and such, using tools like scrapebox.

I think it's called "white hat" more so than "black hat" because it's usually "safe" to do so. i.e., Google will not be able to automatically detect these links which are against their terms of service to penalize them.