Proposition 8, which was passed by voters in November 2008, altered the California state constitution to ban same-sex marriages. It was later declared unconstitutional by a federal court. In 2013, the U.S. Supreme Court ruled that the plaintiffs did not have standing, which allowed the lower court's decision to stand.
According to contribution records on the website of the Secretary of State for California, Eich, who was named Mozilla CEO earlier this week, donated $1,000 in October 2008 to ProtectMarriage.com, a collection of conservative and religious political activist groups. Altogether, ProtectMarriage.com raised $40 million to support the ballot proposition.
On Thursday and within a 15-minute stretch, several Mozilla employees used Twitter to make identical or similar announcements, calling for Eich to step down.
"Like many @Mozilla staff, I'm taking a stand. I do not support the Board's appointment of @BrendanEich as CEO," tweeted Kat Braybrooke, a curation and co-design lead at the firm.
"I'm an employee of @mozilla and I'm asking @BrendanEich to step down as CEO," added John Bevan, who works on Mozilla partnership.
Others who also asked Eich to resign included Jess Klein, creative lead for Mozilla Open Badges; Chris McAvoy, who also works on Open Badges; Sydney Moyer, an engagement and communications assistant; and Dan Sinker, who heads up the Mozilla-Knight OpenNews project.
Paula Le Dieu, a senior director at Mozilla, went one step further: In a short post to her personal blog, Le Dieu said she was taking an unpaid leave.
"I can't walk away from these people [at Mozilla] nor the cause I share with them nor the potential for Mozilla to once again be known as the champion to all but neither can I continue to earn my living from Mozilla while it is seen to exclude and alienate anyone," Le Dieu wrote. "So as of today, I am on unpaid leave."
Eich's contribution to ProtectMarriage.com had made news before. In 2012, the Los Angeles Times reported on a spate of 5,000 tweets on the subject as people lambasted the donation and defended Eich's right to separate his personal and political beliefs from his job.
Eich was Mozilla's chief technology officer at the time, a position he held until his promotion Monday to CEO.
Mozilla did not reply to a request for comment on the Twitter resignation calls, but on his personal blog Wednesday, Eich spelled out his plan for ensuring equality at the workplace and diversity in the Mozilla community.
"I am committed to ensuring that Mozilla is, and will remain, a place that includes and supports everyone, regardless of sexual orientation, gender identity, age, race, ethnicity, economic status, or religion," Eich wrote.
He did not mention his contributions in support of Proposition 8 specifically, but did ask for employees' support. "I know some will be skeptical about this, and that words alone will not change anything," Eich said. "I can only ask for your support to have the time to 'show, not tell;' and in the meantime express my sorrow at having caused pain."
That same day, Mitchell Baker, chairperson of the Mozilla Foundation, and with Eich, co-founder in 1998 of the Netscape project that eventually became Mozilla, also weighed in on the even-then-building controversy with support for Eich.
"Mozilla's commitment to inclusiveness for our LGBT [lesbian, gay, bisexual, transgender] community, and for all underrepresented groups, will not change," said Baker on her company blog. "The CEO must have a commitment to the inclusive nature of Mozilla. This includes of course a commitment to the Community Participation Guidelines, inclusive HR practices and the spirit that underlies them. Brendan has made this commitment."
Gregg Keizer covers Microsoft, security issues, Apple, Web browsers and general technology breaking news for Computerworld. Follow Gregg on Twitter at @gkeizer, on Google+ or subscribe to Gregg's RSS feed . His email address is firstname.lastname@example.org.