We recently added the Debian Iceweasel web-browser to the [libre] repo (actually "iceweasel-libre"), and encourage IceCat users to switch. For a long time our primary browser was GNU IceCat. Both are based on the Mozilla Firefox browser, which we don't include because it recommends non-free addons, encourages the use of non-free Software as a service (Google SafeBrowsing), and has non-free trademark licensing.
From an ideological standpoint, IceCat is the browser we want to use. As part of the GNU operating system, it shares our goals of freedom. However, Giuseppe Scrivano is the only developer working on IceCat, and he is having trouble keeping up, and is looking for a co-maintainer. Unfortunately, this means that there is usually a significant lag between the new version of Firefox and the new version of IceCat. There wasn't even an IceCat 8; by the time the a new version was released, it was based on Firefox 9. When the new releases do come out, each is more buggy; we have long dealt with the bug that tab-restore doesn't work, and version 9 introduced severe lockups and freezes.
Debian Iceweasel is less dedicated to freedom, and exists for two purposes; because of the trademark issues, and in order to meet Debian quality standards. For example, Firefox, and thus IceCat have not supported the MIPS architecture since version 4. This is unfortunate because it means that the mips64el port of Parabola is offering an even older version of IceCat.
Between the time Firefox 9 and IceCat 9 came out, in want of a recent Mozilla-based browser, our sister project, ConnochaetOS wrote a patch for Iceweasel to make it not recommend non-free addons or services, and packaged it as iceweasel-libre.
For several reasons ConnochaetOS's Iceweasel was unsuitable for inclusion in Parabola, so Luke Shumaker (lukeshu) began modifying the PKGBUILD for Parabola. Soon after he began, IceCat 9 came out, so they were worked on together. For a time they were both in [libre-testing].
Iceweasel proved to be stable, and has graduated to [libre]. However, IceCat 9 experienced too many lockups and bugs, and is being held in [libre-testing]. If you are interested in fixing this, and getting it moved to [libre], you should get in touch with Giuseppe on the bug-gnuzilla@gnu.org mailing list.