You can still be anonymous in open source projects. My experience is that nobody cares about your background or ethnicity or (at least) wants to know about your background/ethnicity. If you're a valuable contributor you will be respected instantly. Also if you're serious about wanting to learn (and have a fairly good foundation of basic skills) you will find people willing to help you. So if you're really worried about being discriminated against, but are serious about becoming a better programmer, just stay anonymous on github.