It won't prevent serving HTML with GET forms (although POST forms won't work, and neither will cookies), although a client may very well not understand the docu

It won't prevent serving HTML with GET forms (although POST forms won't work, and neither will cookies), although a client may very well not understand the document (or any other HTML document) and not display it (and even if it does understand HTML, it might restrict HTML with Gemini by default, in order to avoid tricking the user into thinking that one kind of document is a different kind, and/or in order to avoid doing things which are undesirable with Gemini; HTML is probably mostly undesirable with Gemini anyways). If you need an interactive system, then SSH or Telnet might be better, rather than Gemini or HTTP(S). For other things, other protocols will be better, e.g. for communications, IRC or NNTP would help (depending on the kinds of communications). They also mentioned a Titan protocol, for writing to Gemini files.