I guess taking features out of a gamemode and then making you buy them is considered donations, it defeats the purpose
The "exclusive" trails for VIP, Sponsor, and Platinum status are just part of what giving donations will give a person. Sure, they aren't available without donations, but you aren't just paying $5+ for a trail. For example, VIP grants access to a limited area in the prison (plus some exclusive weapons/items, ability to change teams without relying on /jointeam and it's player count limit, optional playtime as the warden, teleporting to yard/free play, etc), a tag next to your name, special weapon(s) on the CTF server, as well as trails.
And I think that giving players an incentive to donate to the server is beneficial and smart. It keeps the server running for those who enjoy it and gives access to special features.
And as for the "stealing credit" issue, he isn't proclaiming that he invented rising lava. He is removing Zapk's name from everything almost in a way to prevent "copyright" issues. In giving an example, it's like a cell phone company taking the iPhone's design, changing some cosmetic/mechanical details, and giving it a new name. They can't get in trouble for it by stealing the name/design now, because it is different now.
Plus, Zapk hasn't said anything about it from what I can tell. If he indeed doesn't care, then why does it matter?