software projects can be hosted here for collaborative development. Nothing dangerous here. Great site, too.
I have used many of their product. Allows me to access my feeds from native applications or web apps. The iphone web app is top notch. NetNewWire for the iPhone is also top notch!
Ruby on rails is a development web framework that has made waves in the web development arena. The site is information with a few screencasts/videos.
Twitter is simply a messaging service. No software to download. Hooks into your SMS or your Jabber IM client.
I can't read the page, but it appears to be a typical typo-squatter format.