In August 1991, Linus Torvalds posted his announcement of what would become the Linux kernel to the comp.os.minix newsgroup. Torvalds was not ideologically aligned with stallman's free software movement — his announcement notably described the project as "just a hobby" — but he initially released Linux under a license that prohibited commercial use, then relicensed it under the gpl-v2 in 1992. This decision, whose full implications Torvalds may not have anticipated, placed the Linux kernel under the same copyleft framework as the GNU tools.
The combination of the Linux kernel with the GNU userland tools produced what stallman insists be called GNU/Linux: a complete, freely available Unix-like operating system. Stallman's position, elaborated in essays and interviews throughout this period, is that calling the system "Linux" erases the decade of work the GNU project contributed and misattributes the philosophical foundation. The naming dispute became one of the recurring friction points between Stallman and the broader free software/open source community.
The gpl-v2, released in June 1991, became the most widely used free software license in history. Where gpl-v1 had addressed specific loopholes, gpl-v2 introduced the "liberty or death" clause — the provision that if a distributor cannot comply with both the GPL and other legal obligations (such as patent licenses), they may not distribute the software at all. This was intended to prevent the GPL from being subverted by patent encumbrances. The version also clarified the "mere aggregation" distinction (bundling proprietary software with GPL software on the same media does not trigger copyleft).
The mid-1990s saw rapid adoption of GNU/Linux in server and technical environments. Ian Murdock founded Debian in 1993, explicitly as a GNU/Linux distribution aligned with free software principles; bruce-perens developed the Debian Free Software Guidelines, which would later form the basis of the Open Source Definition. The free-software-foundation grew as an organization, and Stallman's speaking and writing output increased.
This period also saw the emergence of tensions that would produce the free-vs-open-source-schism-1998-2007 era. Corporate interest in "free" software was growing, but many corporations were uncomfortable with the philosophical framing. Stallman's insistence on "free software" as an ethical position, his willingness to be confrontational about it, and the FSF's strict interpretation of the GPL made some developers and companies look for a different framing — one that emphasized the practical benefits of open development without the ideological weight.