From AnOtherWiki, the free encyclopedia written by, for, and about the Otherkin community.
Alterhuman or alter-human individuals are people who have experiences or an identity which they perceive as being alternative to or outside common societal ideas of humanity. Originally termed Alternative Humanity Personal Identity (AHPI), alterhuman functions as an umbrella term which covers a broad spectrum of other terms and groups; it most often includes otherkin, therian, fictionkin, plural systems, otherhearted individuals, and otherlinkers, but it may also be used to refer to transhumanists, trans-species individuals, furries, daemians, and vampires among others.
Indexed web registries points that the term was coined by Malchior on September 26, 2014  on a Tumblr post.
Due to the large scope and opt-in nature of alterhuman, many public organizations which label themselves as alterhuman include a wide range of different identities in their focus. Some furry organizations have also chosen to incorporate certain furry-adjacent alterhuman individuals, such as therians and otherkin, within their own research as well.
Freedom of Form Foundation
The Freedom of Form Foundation (FFF) is a nonprofit corporation founded in 2018. The FFF funds and popularizes scientific research geared towards morphological freedom, including full-body changes which utilize the appearances or traits of other species. 
The FFF's staff team includes both alterhumans and furries. The organization has also attended multiple conventions and held panels on related subjects:
- WikiFur:Anthro New England 2019 - Panel: Make It Real 
- WikiFur:Anthro New England 2020 - Panel: What if you could actually be your fursona? 
- Midwest Fur Fest 2021 - Panel: "What if you could actually be your fursona?" Freedom of Form: Make it Real.
Alt+H: The Alterhuman Advocacy Group
Alt+H is an alterhuman advocacy group which aims to legitimize alterhumanity in the eyes of the larger public and offered resources for alterhuman individuals. It started as a Tumblr blog in 2016, and ran as a nonprofit organization from 2019-2022. Alt+H announced the dissolution of its LTD and its Patreon in 2022, and resolved to turn its focus away from social media after receiving criticism regarding its #WolfGetsReal Twitter campaign. It continues to operate as an unincorporated, self-funded group.
FurScience is the public website and name for the International Anthropomorphic Research Project (IARP). Founded in 2016, FurScience examines aspects of furry culture through a variety of lenses, including psychological, anthropological, and sociological, with the intent of cultivating better understandings of furries for those both inside and outside of the fandom. 
Although FurScience focuses largely on furry fandom and culture, they have also historically included otherkin and therians within the scope of their research. They also have an in-progress page of their website dedicated specifically to otherkin and therians. Alt+H described FurScience as "conducting research of interest to alterhuman people."
- Malchior. 2014. This will probably be my last post on semantics...
Tumblr.com. https://phasmovore.tumblr.com/post/98482696958/this-will-probably-be-my-last-post-on-semantics. (accessed January 14, 2022).
Archived at https://web.archive.org/web/20180326012554/http://phasmovore.tumblr.com/post/98482696958/this-will-probably-be-my-last-post-on-semantics.
- Mordecai. 2019. Here are some ways you can be alterhuman and...
Tumblr.com. https://vagabond-sun.tumblr.com/post/186964768875/here-are-some-ways-you-can-be-alterhuman-and. (accessed January 14, 2022).
- Alterhuman Advocacy Project. 2019. Alt+H > Educate > FAQ
alt-h.net. https://www.alt-h.net/educate/faq.php. (accessed January 14, 2022).
Archived at http://web.archive.org/web/20200419101550/https://www.alt-h.net/educate/faq.php.
- Freedom of Form Foundation. FFF > About Us > Vision
freedomofform.org. https://freedomofform.org/vision/. (accessed January 14, 2022).
- Freedom of Form Foundation. 2019. Make It Real
youtube.com. https://www.youtube.com/watch?v=nb1Yn-CHql4&ab_channel=FreedomofFormFoundation. (accessed January 14, 2022).
- Freedom of Form Foundation. 2020. What if you could actually be your fursona?
freedomofform.org. https://freedomofform.org/2129/anthro-new-england-2020/. (accessed January 14, 2022).
- Freedom of Form Foundation. 2021. "What if you could actually be your fursona?" Freedom of Form: Make it Real.
twitter.org. https://twitter.com/FreedomOfForm/status/1465319823475462152. (accessed January 14, 2022).
- Alt+H. Alt+H > About
alt-h.net. https://www.alt-h.net/about/index.php. (accessed January 14, 2022).
- Alt+H. 2022. Hey all. It's been a little under three weeks...
alt--h.tumblr.com. https://blog.alt-h.net/post/672487310838956032/hey-all-its-been-a-little-under-three-weeks. (accessed January 14, 2022).
- FurScience. FurScience > Who we are
furscience.com. https://furscience.com/who-we-are/. (accessed January 14, 2022).
- FurScience. FurScience > Therianthropy/Otherkin
furscience.com. https://furscience.com/therian/. (accessed January 14, 2022).
- Alt+H. Alt+H > Research
alt-h.net. https://www.alt-h.net/research/. (accessed January 14, 2022).