I am planning to use some third party libraries, more specifically FreeImage, and in the Download page there is a Disclaimer:

http://freeimage.sourceforge.net/download.html

Basically it displays the licenses and the copyright owners of the libraries included within FreeImage.

I know I have to display FreeImage's license at some point in my game, but do I have to display all of those licenses from the libraries contained within FreeImage itself?

You need to read all of the licences for each library you intend on using. When people "package" a lot of libraries under one roof the license for the package itself doesn't over-throw the individual licences for the libraries included. Find out each library you're using within the package, and go to their original distribution site, you'll find the licence information there.

http://freeimage.sourceforge.net/license.html

For example LibRaw: https://www.libraw.org/docs they list:

LibRaw is distributed for free under two different licenses:

GNU Lesser General Public License, version 2.1

COMMON DEVELOPMENT AND DISTRIBUTION LICENSE (CDDL) Version 1.0

You'll have to do your own due diligence as any mistake will affect you more than any member here.

Thanks Rutin, I think it's better to be safe than sorry.

With the LGPL you can ship a DLL of the library instead of static linking to avoid sharing your code. This is expected practice and not a work-around.

Even if you don't use the LGPL part of FreeImage and wanted to static link, I would go so far as to try and remove all LGPL code completely and build the static library before using it. There may be a preconfigured make option.

Don't even touch GPL code without planning to release the source code to your game. DLL or not.