The new chief executive of Mozilla, the company behind the Firefox web browser, has vowed to be inclusive – despite having financially backed efforts to ban equal marriage in California.

Brendan Eich on Monday was appointed CEO of Mozilla. The American computer programmer and creator of the JavaScript scripting language is a co-founder of Mozilla.

It was revealed in 2012 that Mr Eich donated $1,000 (£605) in 2008 to the campaign supporting California’s Proposition 8, whilst he was Mozilla’s chief technology officer.

The Prop 8 law banned same-sex marriages in the state and was finally struck down by the US Supreme after years of legal battles in June 2013.

In a statement to PinkNews on Wednesday, a Mozilla spokesperson defended the appointment of Mr Eich, saying Mozilla “has always been deeply committed to honouring diversity in sexual orientation and beliefs within our staff and community, across all the project’s activities.”

Mozilla refused to say whether it or Mr Eich supported equal marriage.

However, Mr Eich has now broken his silence. “[It is] my personal commitment to work on new initiatives to reach out to those who feel excluded or who have been marginalised in ways that makes their contributing to Mozilla and to open source difficult,” Mr Eich said.

“I know some will be sceptical about this, and that words alone will not change anything. 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.”

He added: “You will see exemplary behaviour from me toward everyone in our community, no matter who they are; and the same toward all those whom we hope will join, and for those who use our products. Mozilla’s inclusive health benefits policies will not regress in any way. And I will not tolerate behaviour among community members that violates our Community Participation Guidelines or (for employees) our inclusive and non-discriminatory employment policies.”