Share The Seeds is a community, not an organization or business. Some members/traders do offer spores but you are more likely to find seeds, cuttings, and sometimes planted plants.
STS branched off from the DMTNexus long ago because a group of Nexus members wanted a different focus that couldn't simply fit into a single subforum or thread. STS was similar to a few other websites like botanicalswap but essentially because they were a tight knit community they survived whereas other message boards lost popularity due to a lacking of interest and activity. (robots also flooded some of these to a degree that destroyed the community beyond repair).
STS is not like any other ethnobotanical message boards. You can't talk about dried plant material, the experience of the entheogen, increasing alkaloid content, etc. These rules are meant to protect the community from being seen as a gray market group. They are probably the most selfless and genuine message board i have ever known. I have also learned so much about growing these botanicals, their plant history and culture, and just all kinds of stuff.
Like the Nexus you have to be promoted to full membership but it's incredibly easy to get promoted in STS whereas the Nexus is like the harvard of Entheogen boards; many are called, few are chosen. All you really need to do is to not exploit the community. Make a few genuine posts that contribute to conversations, post pics of your plants, understand their rules and guidelines, and generally just be a productive member of the STS society.
Currently there isn't a whole lot of mushroom or fungi spores circulating STS. I personally managed to source reishi spores. As far as entheogens, food sources, and medicinal plants go i have been able to source a very great amount of food sources (specifically i'm quite enthusiastic about the ghost chilli's!), several medicinal plants, quite a few very interesting entheogens (kratom, kava, acacia's, mimosa hostillis, sacred cacti seeds, various smoking herbs, sinnasuichi, and just all kinds of stuff!).
Anyways I strongly recommend these guys. Furthermore i recommend even more so that anyone with any medicinal or edible mushrooms to donate spore prints, liquid culture, and various mycology supplies. so that they can be grown and so that spores can be collected and distributed to others who then in turn grow and collect uncontaminated viable spores. Much of these mushrooms are under-circulated.
it is a bit disappointing that STS doesn't offer Psylocybin spores for mycroscopy but generally it's probably the best place to ethically source seeds and cuttings and learn about the plants that shall grow thereof.
Sharing is caring! :) So share, share, share! i swear... Hair. Pear. Stereotypically rhymed word.