Seems like they designed an alorithm/a software to harvest BTC on other people's computers. Part of that design was done by another algorithm they call "artificial intelligence" because it's a cool buzz word.

That's actually not that uncommon anymore. You just deliver a website that loads some javascript, which executes code that computes BTC.
You'll find that a lot on fishy websites nowadays. A dead giveaway is your CPU usage skyrocketing for no apparent reason.

It's basically the old SETI@home idea of distributed computing, just in a web browser instead of using dedicated client software. Only now you're not dedicating your CPU power to a scientific cause, but to earning money.

According to the claims of this project, the main difference to other, fishy browser miners is, that this time you're not cluelessly earning money for someone else, but wilfully for yourself.
I'm not sure whether that's actually possible. Due to the relatively high electricity costs in Germany, mining BTC here with conventional computers doesn't reach a break-even point for quite some time now.

I guess "unusual" in this case means the average Joe, anyone who doesn't have the knowledge to understand the principles of blockchain currencies or to set up dedicated software for mining it.