Are you sure it is optional? [1] In any case Mozilla does offer them. So what exactly is the problem? What would change with or without gay marriage recognized by California? If anything, this shows that while Eich may be opposed to gay marriage, he is not at all opposed to equal benefits (unless of course you could point to instance where he tried to remove that policy).

[1] https://en.wikipedia.org/wiki/Domestic_partnership_in_Califo...