Is it better to use threads or fork in the following case

[CTO]

> In addition, the zip file format stores the directory at the end of the  
> file. So you can't process it until it's completely downloaded.  
> Concurrency doesn't help here.

Don't think that's relevant, if I'm understanding the OP correctly.
Lets say you've downloaded the file once and you're doing whatever
the app does with it. Now, while that's happening the half an hour
time limit comes up. Now you want to start another download, but
you also want to continue to work with the old version. Voila,
concurrency.