If you prefer to go home and do other things than code, you may want to reconsider joining a company where everyone probably feels the opposite way. By making a github account a required field, they are pre-weeding out individuals they feel do not fit into their culture. Make sure you are willing to be that outsider if you try and work around that.

But, if you feel these companies are still a fit for you, I would try and get references from the startups you've helped; have them vouch for you in lieu of sample work.