License clarification?

The LICENSE file says this:

The Nice Glib ICE library is licensed under both the Mozilla Public License
version 1.1 and the GNU Lesser General Public License version 2.1. For the
full text of these licenses, see the files COPYING.MPL and COPYING.LGPL
respectively.

There was some confusion about the meaning of this in the MacPorts project (https://trac.macports.org/ticket/69760#comment:6), so I'm asking here in hope of clarifying:

Does the statement in LICENSE mean that you can use libnice under the terms of the LGPL or the MPL (my interpretation, and the interpretation of Arch Linux); or does it mean that you have to abide by both the terms and restrictions of the LGPL and MPL (the MacPorts team's interpretation)?