I can't entirely guarantee that they'll absolutely always work exactly as they should, so it's probably not the best idea to use them in anything absolutely mission-critical. That said, they do seem to work fine for me wherever I use them. And if you do find something wrong, open an issue on GitHub and I'll do my best to fix it.
These scripts are licensed under the ☺ licence, so basically you're free to use them however you please - feel free to use or modify them in whatever way you like. You don't have to explicitly credit me (but if you do then I won't complain), but just don't pass them off as entirely your own, ok? That's just not cool.
To begin with, because I needed a smallish MD5 that wasn't poorly written (lots of the others out there leaked globals), but nowadays it's pretty much just because I can.
Well, I started out with a mashup of the pseudocode on the respective wikipedia pages for the functions along with helper functions I found somewhere on the internet for converting strings to byte arrays etc, then bashed them every which-way I could with functionally-equivalent rearrangements to make the size smaller however I could think. Just don't try to get me to explain what any of it does any more.