I second the suggestion not to run Freenet off the SD card. This did indeed kill the poor little card in a month's time.
I used Berryboot to install Raspian such that it runs off a USB SSD. This setup has been working well for over a year.
Raspian has the advantage of already being set up with the Oracle flavor of Java. I haven't had much success using the open source version of Java that most Linux flavors come with.
My Raspberry Pi 3 handles most of what you want from Freenet well. You can of course view jSites. You can insert your own jSites. You can install and use FMS. You can upload and download files.
The Raspberry Pi 3 does not seem to have enough power to run the Web of Trust required for Sone and Freemail and the convenient blog programs that depend on it. The WoT plug-in constantly crashes and is unusable. The WoT variant built into FMS does not cause problems.