Mario Party 64 appears to be either a completely separate fan-made game inspired by the Mario Party series or a substantial mod of an existing N64 game that reimagines it as a Mario Party experience. Either way, this showcases the passion of developers aiming to recreate or enhance the Nintendo Mario Party formula in a new form.  Nintendo holds the rights to the original series; this is a different product inspired by it.

Mario Party 64

Mario Party 3 Character Modpack! (Toad, Bowser, B. Bowser)