If you have or know any more, please comment!
For the Toyhou.se world: UniversalSpecies run by Nobody , which also lists Semiclosed and Closed Universes!
Other words for "Open Universe" include:
Beings who belong to these worlds are able to go to other worlds and interact with the beings that live there without it being "non-canon", aka the species owner isn't going to say "That's impossible.". It may or may not be difficult to go between such worlds, but it is possible. Only open and semi-open universes will be listed here.
This is by no means a comprehensive list of every open universe on dA. There are many others, most of which do not actually say "open universe" anywhere, because the term "Open Universe" was just invented. Just as a cat is "un chat" whether or not you speak French, an original species that can meet other original species characters exists