This is the best text editing program exclusively for the Mac. Use it as a replacement for the TextEdit that comes with Leopard. It does everything you need and more. This version does not require a serial or reg code. It is pre-keyed. Just drag it into your Applications folder then on to your dock. Set it up as your default text editor (through the Get Info menu button).
Created by a closet UNIX geek who was lured to the Mac platform by its ease of use and elegance, TextMate has been referred to as the culmination of Emacs and OS X and has resulted in countless requests for both a Windows and Linux port, but TextMate remains exclusive for the Mac, and that is how we like it!
BTW, if you upgrade this app then you'll have to purchase a serial.