Bruce Perens is a programmer and open-source activist who led the Debian GNU/Linux project and co-founded the open-source-initiative in 1998 with eric-raymond. He authored the Debian Free Software Guidelines, which became the basis for the Open Source Definition — a document closely derived from stallman's free-software-definition.
Perens's arc is notable for its partial return toward Stallman's positions. He co-founded OSI partly as a pragmatic marketing exercise, but later expressed discomfort with OSI's embrace of licenses that do not enforce copyleft, and with the broader drift of "open source" away from the ethical commitments of software-freedom-vs-open-source.
The Debian project itself occupies an interesting position relative to stallman: Debian's Social Contract commits to free software, and the project has maintained the free-software-definition as its guiding standard. Debian officially calls its operating system "Debian GNU/Linux," partially satisfying Stallman's gnu-linux-naming preference.
Perens appears in revolution-os-documentary and is discussed in free-as-in-freedom-williams and rebel-code-moody as part of the open-source-definition-schism era documented in free-vs-open-source-schism-1998-2007.
His trajectory — from OSI co-founder to critic of OSI's direction — illustrates the tensions within the software-freedom-vs-open-source debate that stallman has consistently highlighted.