It says "Mozilla" right beside his name. I think most people would have less of an issue of he donated without stating his employer.

In the US, currently, if an individual donates more than $200 to certain types of political campaigns, that individual's name, address, occupation and employer must be included in campaign finance disclosures. $1000 > $200, so that's why the information is there.

As an aside: my previous job was in journalism, and generally in that field there's a (self-enforced) ethical code against making such donations largely because the employer's name is disclosed and could lead people to assume endorsement by a news outlet.

I don't know much about the law here, but isn't it required that you make such information public? That is, isn't that part of how campaign donations are tracked and regulated?