From what I read in the license, such actions are explicitly intended to be taken. The contributors accept that when they license their software under MPL. Of course, the product must include the license in Exhibit A to even be legal (presumably you are not interested in the ethics of illegally renaming the product). That exhibit is:
"The contents of this file are subject to the Mozilla Public License
Version 1.1 (the "License"); you may not use this file except in
compliance with the License. You may obtain a copy of the License at
Software distributed under the License is distributed on an "AS IS"
basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See the
License for the specific language governing rights and limitations
under the License.
The Original Code is ______________________________________.
The Initial Developer of the Original Code is ________________________.
Portions created by ______________________ are Copyright (C) ______
_______________________. All Rights Reserved.
Alternatively, the contents of this file may be used under the terms
of the _____ license (the "[___] License"), in which case the
provisions of [______] License are applicable instead of those
above. If you wish to allow use of your version of this file only
under the terms of the [____] License and not to allow others to use
your version of this file under the MPL, indicate your decision by
deleting the provisions above and replace them with the notice and
other provisions required by the [___] License. If you do not delete
the provisions above, a recipient may use your version of this file
under either the MPL or the [___] License."
It also states that "You must include such notice in a location (such as a relevant directory) where a user would be likely to look for such a notice." If superdb.com does this, then it does exactly what the contributors expected it to do. By doing so, the original contributors get the credit they expected from the license.
Now perhaps this particular open-source database software was unaware of what their license choice meant, in which case such actions might be preying on the ignorant. But if we assume they knew what they were doing, they picked this particular license out of the dozens of similar licenses which draw the line slightly differently. There was intent to support this action. Thus, to argue that such an act is unethical is to argue that the act the contributors intended you to do is unethical. While you could argue that there are sufficient negative consequences to make it unethical, doing so with the contributors expressed intent is a difficult argument to make. You would likely have to argue that the contributor's choice of license was also unethical, because it provided too much freedom and not enough guidance.
(assuming this action is actually legal. The way I read the license, it's legal, but a lawyer may know better than I)