Pidora is Fedora 20 based, Fedora 20 is in EOL (End Of Life).
yum does not update anymore
Is it still safe to use Pidora for hosting a webserver or fileserver?
Pidora stopped being updated at least a year ago; I could go check my logs to be sure, but it was well before F20 reached EOL. I also had an x86-64 F20 system up for the duration and it was receiving updates during that time. This implies it was abandoned by the maintainers before F20 got to EOL, as does the state of their web page and the fact the Foundation stopped listing it. Pidora was the product of a university based research group. Presumably they moved on to other things and none of those involved wanted to take responsibility in their spare time.
That said, it doesn't make it particularly unsafe to use, it just means you won't be getting any security updates. I believe it is, e.g., safe from heartbleed but probably not shellshock. If you are running an outward facing server, it is always a good idea to periodically check the upstream distribution site (i.e., the homepage) for relevant software to see what news they have about this kind of thing, because using a current distro doesn't guarantee anything.
I'd still recommend against using it for anything at this point as it isn't being maintained.