The donation to the cause supporting Proposition 8 in the 2008 Presidential election was first picked up online in 2012, and Eich said on his blog back then admitting to the donation, but rejecting allegations of hating gay people. He said at the time that Mozilla was a diverse organisation with differing views amongst all its employees.
His appointment as the new CEO for the company, after nine years as its chief technology officer, brought back the issue of his donation to the cause, despite Proposition 8 ultimately being ruled unconstitutional by the Supreme Court in 2013.
In a blog post today, Hampton Catlin, the creator of Wikipedia Mobile, CSS extension language Sass, and CEO of rarebit said he would no longer develop apps for Mozilla's Firefox web browser given Eich's support for banning same-sex marriage.
"As a gay couple who were unable to get married in California until recently, we morally cannot support a Foundation that would not only leave someone with hateful views in power, but will give them a promotion and put them in charge of the entire organisation," he said.
He said he wouldn't have been able to have started his new company, rarebit, with his husband Michael, while Michael was still on his work visa, and unable to get married. He said Eich had two years since the news of the donation to recant his views, and he said that given Eich's silence, he is unable to continue to support Mozilla.
"By the very bones in our body, we cannot dare use our creativity, experience, knowledge, and passion to further the career of a man who has to this day not apologised for his support. I can't spend hours and days and years polishing, building, and upgrading applications that make him richer than he is," Catlin said.
"Building great apps is what we love to do, it's our passion. We want to make great things for people to use. Whether it's a fun little puzzle game, or a useful dictionary, or our work on Sass."
In a statement, Mozilla said it was committed to diversity in its organisation.
"Mozilla has always been deeply committed to honoring diversity in sexual orientation and beliefs within our staff and community, across all the project’s activities. One concrete example of this is in our health benefit policies. Mozilla provides the same level of benefits and advantages to domestic partners as we do to married couples across the United States, even in states where it is not mandated," the organisation said.
"For those who choose life insurance, voluntary spouse coverage extends to domestic partners, including same-sex couples. With thousands of people spanning many countries and cultures, diversity is core to who we are, and we’re united in our mission to keep the web open and accessible for everyone."