Iceweasel

Iceweasel was a free and open-source web browser based on Mozilla Firefox. It was developed and maintained by the Debian Project. The primary reason for the fork from Firefox was to comply with Debian's strict free software guidelines, which required that all software in the main repository be free of any non-free components, including trademarks and branding. Mozilla's Firefox had, at the time, included non-free elements such as artwork and the Firefox name itself, which were not considered strictly free software by Debian's standards.

Therefore, Iceweasel was essentially Firefox without the proprietary branding and with all non-free elements removed or replaced with free alternatives. This allowed Debian to distribute a web browser that was functionally equivalent to Firefox but met their free software requirements. Over time, the relationship between Debian and Mozilla evolved. Mozilla began to make more of Firefox's components available under free licenses, and the branding issues became less of a sticking point.

In 2016, after many years of existence, Debian announced the reintroduction of Firefox into its main repository, effectively marking the end of Iceweasel. This decision was made possible by renewed collaboration with Mozilla and changes in how Firefox was packaged and distributed. While Iceweasel is no longer actively developed or maintained by Debian, it remains a notable example of how free software communities adapt and modify existing software to adhere to their principles. Users who previously used Iceweasel would have transitioned to Firefox or other compliant browsers.