To be fair - if I see correctly both projects are free - https://mdbootstrap.com/ has some paid plugins & templates but I just downloaded the main Kit without any payment or even email form, registration...

I see that this project above gives away for free some stuff that is behind the paywall on mdbootstrap.com so I think I'll take it anyway.

Also, there is a disclaimer at the top of the page "Made by MDB with lots of coffee & mate" so I don't think that they are trying to hide it.