The [NCRP] tag has been added for Non-Canon RolePlays. Non-canon roleplays are roleplaying threads that are not part of the shared setting (although they may be based on it). Events in NCRP threads don't affect the rest of the setting, usually because they contain elements deemed incompatible with the main setting. For example, the World War 2 RP thread going on right now has the NCRP tag because it's set in WW2, not the Star Army universe.
Update: I changed this forum's settings so it only shows threads that have been active in the last two months, and hides the older ones. They're still there, just not immediately visible. This keeps people from seeing threads of inactive RPs. If you want to see older stuff, simply use the link that says "Click here to display older threads." or use the thread display options. I'm also doing this with the Open RP forums.