Why does FirefoxPortable phone home?

I've been experimenting with FirefoxPortable run locally and according to my firewall, the firefox.exe it launches tries to connect to portableapps.com every time it starts, although I have set the home page to blank and turned off all the firefox options that would likely result in automatically contacting external servers (e.g. phishing checking, auto update checking). Call me paranoid, but I'm not a big fan of apps that silently "phone home" - can anyone tell me for what purpose the firefox binary launched by FirefoxPortable is trying to contact portableapps.com?

Thanks.