Leonard "Len" H. Tower Jr. (born June 17, 1949) is a free software activist and one of the founding board members of the Free Software Foundation,[1] where he contributed to the initial releases of gcc[2] and GNU diff.

[5] As the FSF's first full-time paid employee, Tower mostly performed administrative tasks, including managing mailing lists, newsgroups and requests for information.

"[9] Stallman released his new GNU C compiler March 22, 1987,[10] acknowledging others' contributions, including Tower's, who "wrote parts of the parser, RTL generator, RTL definitions, and of the Vax machine description" based on ideas contributed by Jack Davidson and Christopher Fraser.

[2][11] Along with Mike Haertel,[12] David Hayes[13] and Stallman, Tower was also one of the initial co-authors of GNU diff, a file comparison utility based on a published algorithm[14] by Eugene Myers.

[15][16][17] During the late 1980s and early 1990s, Tower spoke at USENIX conferences as a representative of the FSF.