Would you know of any haskell text://protocol clients? Or servers? [1][2][3]

I may be wrong, but it appear so me that

• This is a newly developed idea
  
• And by "newly" I mean none of the git repositories you shared is more than about a month old, including the one containing the website
  
• All appears to be done by a single, anonymous enthusiast
  
• None of the resources explain the "why", or a use case, or seem to contain much beyond example/filler content
  

So I don't see a reason why there would already be a Haskell server and/or client, as the single developer seems to follow a different route right now.

In fact if you told us you're actually the one behind this idea, posting the question as kind of guerilla marketing, I wouldn't be surprised. Not insinuating you are though, or that that would invalidate the idea. (If nothing else, invalidate :: value → value; the value of this protocol is neither obvious nor explained, and applying a relative value-changing function like invalidate to undefined input must necessarily also return undefined. ;) )

In other words if you're enthusiastic about this there's a good chance you can be the first! ;)