He is one of the founders of the Electronic Frontier Foundation, the Cypherpunks mailing list, and Cygnus Solutions.

An outspoken civil libertarian, Gilmore has sued the Federal Aviation Administration, the United States Department of Justice, and others.

He was the plaintiff in the prominent case Gilmore v. Gonzales, challenging secret travel-restriction laws, which he lost.

As the fifth employee of Sun Microsystems and founder of Cygnus Support, he became wealthy enough to retire early and pursue other interests.

The Bootstrap Protocol evolved into DHCP, the method by which Ethernet and wireless networks typically assign devices an IP address.

Gilmore protests that his mail server was programmed to be essentially useless to spammers and other senders of mass email and he argues that Verio's actions constitute censorship.

[9][10] He unsuccessfully challenged the constitutionality of secret regulations regarding travel security policies in Gilmore v.