Any links to general rules, for those who are first time here and don't know what "RaNGE" is?
Although DLS basically explained it, I'll just go into slightly more detail.
In Rika and Nitori's Garage Experiments, there will occasionally be contests, as seen in
the Info/FAQ thread. In these contests, which are hosted by a denizen of RaNGE, the theme can vary depending on time of year, the person doing it, etc.
Generally speaking, contests marketed as official 'RaNGE' contests already have a number of guaranteed participants at startup and tend to have a very specific base set of unwritten rules, including but not limited to:
-There is a requirement for minimum and/or maximum number of attacks
-Touhou characters are required (depending on the theme)
-All attacks must be in-character (depending on the theme)
-The overall aesthetic of your script must fit with the theme of the contest
-Danmaku quality is the most important aspect of your script
etc.
Anyone can host a contest here, but there is definitely a responsibility aspect that is required of all hosts. Hosts are allowed to participate in their own contests. The main job of the host, once they have decided to make a contest, is to select the judges and deadlines, address participant concerns, make sure rules and guidelines are clear, and, at the end, make sure that the judges are doing their job.