While this works for freelancers/students/startupers, it doesn't work very well for people working in bigger companies. If your interests are related to your day job, I think it's quite risky to put your code on GitHub, even if the code is not "official". While I do have a GitHub account with some code in it, that code is not really representative. If having a relevant GitHub account becomes a pre-requisite, you may…
Wasn't a big deal in the end, I just made sure it was using a commercial friendly license, but you do have to take care.
If it was a US employer they may have sued me if they didn't think that the OSS code came before the inclusion in the product (which it did).