One problem you're likely to encounter is that both richfaces & primefaces download jquery to the client,
so I would imagine that the last one downloaded would be the one that gets used, but would it be compatible
with the other library (assuming different versions)?
You might find that the 'double click' problem goes away if you put the file upload component in it's own
form, but even then if you get it working it's likely to be more by accident than design imho.
It is in its own form and there are no PrimeFaces components on this particular page. I guess that some work on PF and RF compatibility has been done and maybe this is a bug in the dev build. I know that both RF and PF use JQuery and maybe there is some workaround to make this work...