Hello. 
My name is Sean and I’m the owner of ZeoWorks which has made multiple indie horror games such as Slendytubbies, Midnight man and Error #53. I have been a massive fan of the halo series since Halo 1 was released. Anyway, me and my team have been discussing wither or not to create a fan-made halo mmorpg in the mid-future. We have read through the ‘game content useage rules’ and will happily follow them. Many websites such as halomaps.org have models ripped out of other official Halo games and I was wondering if we are allowed to use them in any way, shape or forum? Such as to use as actual 3D models in-game or use rendered images of 3d models (such as a grunt for example) as templates whilst creating our own 3d models. Thank you!
~Sean
As far as I know, using pre-existing assets is not a good idea.
As long as all assets are of original design and creation, I don’t think you’ll have many problems, as long as you follow the Fair Use clause of the copyright act.
Although, if Microsoft is still optioning a potential Halo MMO itself, they may can your fan project due to competition concerns.
Source: I’m a third-year Game Development student preparing to be ejected into the industry.
Thank you for your response Gruntsworthy. So using models just as they would possibly be safe? No minor edits to them? And I believe Microsoft cancelled the Halo MMO project over 7 years ago so we should be safe on that ground, not to mention of course it is for non-commercial use.