The History of IceWeasel
This article intends to clarify some of the confusion related to the IceWeasel and IceCat web browsers, their origins, and history. Throughout this article, the names IceWeasel/Firefox will be used; but for the most part, the article applies to IceCat/Firefox-ESR, IceDove/ThunderBird, and IceApe/SeaMonkey as well.
The most common misconception is that IceWeasel is a web browser project that originated and was maintained by Debian; and that other IceWeasels are forks of the Debian project. Now that Debian no longer has a browser named IceWeasel, that misconception leads people, who know of IceWeasel only as a Debian program, to assume that "the IceWeasel project" is unmaintained legacy abandon-ware; and to be skeptical and inquisitive as to whether the Parabola "fork" is up-to-date and properly maintained. That concern is misplaced though; because it is not really a fork - it is always built from the current Mozilla source code, and rebuilt as new Mozilla versions are released.
The simplest explanation of why that concern is misplaced; is that it is not quite appropriate to call IceWeasel a "project" at all, or even a distinct web browser fork. IceWeasel is just Mozilla Firefox, with certain features disabled, and a different name and artwork (branding) applied. Most of those features are disabled, simply by setting a flag in a configuration file before compiling: e.g. '--disable-eme'. A fork would imply a unique development path, with significant (and typically incompatible) changes to the source code, usually kept in a separate repository, containing the complete source code. That level of separation and the on-going maintenance could be considered as a distinct project, separate from the upstream development team. However, the Mozilla sources are highly configurable; so variants with significantly different feature-sets can be compiled without making any changes at the source-level. If IceWeasel is any sort of project at all, it is only the branding package: the name and artwork; and that requires little maintenance. That adorable lil' ermine is a very low-maintenance pet to keep.
So, Parabola IceWeasel is not a fork of Debian IceWeasel; in the same way that Debian IceWeasel was not a fork of Mozilla Firefox. In both cases, the software is Mozilla Firefox; but compiled in different configurations. The Parabola differences (such as disabling DRM) are primarily to meet the FSDG; and furthermore, to enhance privacy beyond the FSDG (such as the 'iceweasel-hardened-preferences' package). The Debian and Arch configurations are barely (or not at all) distinguishable from Mozilla Firefox. For the most part though, whenever the version numbers correspond, they are all barely distinguishable from each other.
As for the origins of the name and artwork, the name was originally coined by cartoonist Matt Groening in 1986. In 2004, Nathanael Nerode suggested it as an alternate name for Debian's web browser, on the 'debian-legal' mailing list. In 2005, the Gnuzilla project adopted 'IceWeasel' as the name of the new GNU web browser; and in 2006, Debian adopted 'IceWeasel' as the name of the standard Debian web browser also. The Gnuzilla developers considered them to differ significantly in features though; and so to avoid confusion, it was decided to rename the GNU browser to 'IceCat' in 2007. The IceCat and IceWeasel Wikipedia articles cover the historic events in more detail.
The original GNU IceWeasel had no unique branding artwork; but used the generic "unbranded" branding. The adorable lil' ermine, that we have all come to know and love, was authored by Ricardo Fernandez Fuentes for Debian's IceWeasel. A few years later, Parabola and Connochaetos adopted the IceWeasel name and the Debian artwork for their browsers.
When Debian was using the name: IceWeasel, it was essentially just a re-branded Firefox. The feature-set was never any different from the Mozilla releases. That is, Debian did not disable or add any features; but some patches were applied occasionally. Essentially, Debian was maintaining a Long-Term Support (LTS) release of Firefox, analogous to what Firefox-ESR and IceCat are today; but this was several years before Mozilla maintained an LTS browser. From the user's perspective, only the names and logos were different; but Mozilla considered those changes to a frozen version, to be outside of their trademark policy, requiring Debian to re-brand their browser. In 2016, Debian reached a reconciliation with Mozilla, concluding that the Debian modifications were not significant enough to require re-branding. Soon afterward, Debian stopped applying the IceWeasel branding, and has been calling their browser: "Firefox-ESR" ever since.
The Gnuzilla, Connochaetos, and Parabola web browsers however, were and still are, re-configured significantly more than the Debian IceWeasel was, in order to meet the GNU guidelines. That is the primary reason why Gnuzilla, Parabola, and Connochaetos still refer to their web browsers as something other than: "Firefox".