That site does not readily provide hashes for their binaries (MD5, SHA512, whatever), and the page is smeared with ads. There's no way to know if the site is trustworthy.
And, anyway, where would I get the trustworthy hashes? They'd need to be communicated to me, directly from the horse's mouth. I'd need to visit ftp.firefox.com, to find out what the correct hashes are in the first place, and then check them against the binary download I receive from your site.
The link you should have provided was:
http://sourceforge.net/projects/portableapps/files/Mozilla%2...
Version 25 isn't listed there yet.
All of this is even less convenient than digging for and deciphering the meaning of Firefox's official downloads.
Also, I see the hash right there on the page: http://puu.sh/530kX.png
Take a look again over the weekend. They are completely FOSS and all their bundling and bundled packages are transparent.
The entire project is voluntary, and it usually takes a day or two from the official release dates, before the volunteers bundle, test, and release the portable application to the general users.
The concept of PortableApps has been simply amazing! (FWIW, I donate to this project too, it's been really worthwhile having the platform).
I have begun to adopt this mechanism for some of my software maintenance strategy. Nowadays, I test the latest version of the updated "PortableApp" on my local copy on my machine first, and if all works well post-update, I ask others to choose the update. Else I simply tell them to uncheck the update until I can confirm that existing functionality remains unbroken. :)