There are two issues with this.

1. It excludes developers who have managed to find jobs that are sufficiently challenging, difficult, and interesting that their jobs keep them fully occupied, and so they simply do not have the time or energy left over to contribute to a bunch of open stuff on Github.

2. What happens after you hire someone? Do you have any policy to ensure that the job won't take too much of their time, or won't be too challenging and interesting, so as to leave them the time and energy to continue working on various open stuff on Github?