IceWeasel
I doubt PortableApps would ever get in trouble for using Firefox's artwork (since it's using the name, too) -- but just in case it might be nice to have this option as well.
"IceWeasel is the GNU version of the Firefox browser. Its main advantage is an ethical one: it is entirely free software. While the source code from the Mozilla project is free software, the binaries that they release include additional non-free software. Also, they distribute non-free software as plug-ins. (IceWeasel does keep the triple licensing used by Firefox to facilitate the reuse of code.)"