Package palemoon (AUR) is installed via its PKGBUILD by compiling sources from ""
https://github.com/MoonchildProductions/Pale-Moon# tag=${pkgver}_Release"".
Package palemoon-bin (AUR) is installed via its PKGBUILD as binary from source ""
http://linux.palemoon.org/datastore/release/palemoon-$pkgver.en-US.linux-x86_64.tar.bz2"".
But the upstream's tarball (
http://linux.palemoon.org/datastore/release/palemoon-27.7.2.en-US.linux-x86_64.tar.bz2) can be extracted anywhere you like, then just execute the "palemoon" file inside it, that's all. No pminstaller is needed, no /opt folder is created. Palemoon can be even run from any other distro after mounting a partition with its folder (tested on Gentoo and PuppyLinux). Certainly, as palemoon package is not created, pacman will not manage it, but the palemoon process is shown by conky or htop. But in this way, any binary can be compiled to run on any linux system.
As to "be floating around the system", here the output
[root@ lx vn]# find / -name '*palemoon*'
/home/vn/palemoon
/home/vn/palemoon/browser/searchplugins/duckduckgo-palemoon.xml
/home/vn/palemoon/palemoon-bin
/home/vn/palemoon/palemoon
[root@ lx vn]#
And "~/.moonchild productions" is also created.