The code is open source, so he can use it how he likes, that's part of the philosophy of open source. If he wants to use Mint as a base to make money off then he is perfectly entitled to that.
Where there might be an issue is him using "Mint" as part of the distributions name. I'm guessing Mint is copyright of Clem and he therefore gets to decide who can and cant use it. If I was Clem I would step in here and sort this out, because its only going to lead to confusion for people.
In fact, when I read the announcement headline at a glance I thought Mint KDE had finally been released, then I read it properly and realised it was some random guys version of a KDE based Mint. I think that is the damaging part. The fact that this could be confused with an official sanctioned community version of Mint when its not.
In fact the more I think about it the more I think its bad that someone else is using Mint in the name of their unaffiliated, unofficial version of the distro. I'm gunna forward this post onto Clem.
In the mean time, what can you do if you don't want to support this distro? Just ignore the guys posts.