...which has nothing to do with NASA the US government organization, or the NSF (FYI). It's just some independent streamers who apparently know you can't get trademark claims against you by the federal government.
NSF was started by Chris Bergen, a meteorologist by trade and a space exploration enthusiast, in early 2000s as a hobby forum (good old phBB) for people to chat about space and rocketry. I'm sure he couldn't even dream about becoming so popular so he didn't spend too much time coming up with a name (ie to protect himself against copyright infringement lawsuits). In fact I'm sure he would love to change the name now as they try to cover space programs all over the world (it's too late as people know them as NSF).