[skkbits]

>"We should hire mid-tier developers based on code review, typically based on open-source code."

While I agree with sentiment this is not always possible. Company I work for, strongly "discourages" to sharing any code outside organization and also open source contributions.

Its not hard and fast requirement but recommendation to avoid code leak and sort of saying we might re-consider your job in passive language.

I know tons of companies right in SF who have "ultimate secrecy" for coding and also what they can contribute to open source.

There is no possible one solution for this problem.