I do realize that. However, in the case of 0ad, they do not require such a CLA. Rather their website has this to say:
> By sending in a patch, you agree that it is your own work (or else make it clear where it came from) and agree to licensing any code as GPL 2+ (or in some cases MIT, especially for code in lib/ - check the existing copyright headers on the source files you edit) and data files as CC-BY-SA 3.0.
> By sending in a patch, you agree that it is your own work (or else make it clear where it came from) and agree to licensing any code as GPL 2+ (or in some cases MIT, especially for code in lib/ - check the existing copyright headers on the source files you edit) and data files as CC-BY-SA 3.0.