It can be either official or fan made parts, but I would prefer the former. I especially need the uniter parts for my G2 MOCs.
Check out the DCC Project:
The Google Drive link contains stud.io files of virtually every Bionicle model you could imagine, and they contain a bunch of Bionicle parts not in stud.io., which you can then copy to your computer. There should also be some links to parts packs somewhere, to download the parts directly.
Additionally, if you search around the community (or even just these message boards), there are also a whole bunch of part packs shared here directly.
The only official parts are the ones that come with stud.io; everything I mentioned above in fanmade.