[Shotwell] contribution copyright

[Xavi]

Hi all,
this email would be slightly different from the others. For my studies I 
have to do some work about free software contributor copyright.

I've been checking yorba website and I haven't been able to find 
anything about copyrihgt disclaimer o assignments for Shtowell projecte 
(or others). How yorba manage contributor copyrights in shotwell? 
Example, if I get some code to yorba to be used in shotwell, is this 
code belonging still to me? Or the code becomes yorba copyright?

Thanks

Xavi