* Do they have their own projects or do they contribute to others?
* How interesting are those projects generically and in the context of what I would need this developer to do?
* Are these projects actually used by anyone? Are there pull requests, etc?
* Does the developer actively keep working on existing projects or move around? I.E., are these learning vs hobby vs commercial?
* How is their readme? Does it exist? Is it sufficiently complete to convey meaning?
* How is the code organized? Is it reasonably laid out? Do they make use of third party packages and tools? Does it seem like they are re-inventing the wheel?
* Does the code work?
* Is the language chosen the right language for the job? Are they using idioms of that language or more generic ways of expressing loops, vsriables, etc.?
* How extensible is their design? Does it feel krufty or is it a pleasure to read?
* Is the code novel? Are they re-inventing the wheel or are they actually fulfilling a need?
* Are their projects wide and varied in scope and tools?
Those are a few things off the top of my head. Not an exhaustive list.
As long as you understand idioms, programming paradigms in general, and good patterns in specific languages (e.g. list comprehension in python, prototypal inheritance in js, metatables in lua, etc.) you shouldn't be afraid of showing off your stuff in X language.
I know good Java developers that have become really good front-ends.
Well Java doesn't have a stigma attached to it like COBOL or BASIC does. What about those of us who have terrible QBASIC code they wrote when they were 14 on their github/bitbucket/etc profiles? I'm not going to hide that; it's public because it's useful. (I intend to dig up more terrible code I wrote and put it up)
* How interesting are those projects generically and in the context of what I would need this developer to do?
* Are these projects actually used by anyone? Are there pull requests, etc?
* Does the developer actively keep working on existing projects or move around? I.E., are these learning vs hobby vs commercial?
* How is their readme? Does it exist? Is it sufficiently complete to convey meaning?
* How is the code organized? Is it reasonably laid out? Do they make use of third party packages and tools? Does it seem like they are re-inventing the wheel?
* Does the code work?
* Is the language chosen the right language for the job? Are they using idioms of that language or more generic ways of expressing loops, vsriables, etc.?
* How extensible is their design? Does it feel krufty or is it a pleasure to read?
* Is the code novel? Are they re-inventing the wheel or are they actually fulfilling a need?
* Are their projects wide and varied in scope and tools?
Those are a few things off the top of my head. Not an exhaustive list.