It's included in the newest Half Life patch and with the newest Radeon Drivers, it's automatically enabled. If you're running the original Radeon (7000, 7200, 7500, Radeon DDR 32mb, Radeon DDR 64mb, Radeon LE, Radeon VE, AIW Radeon, etc) all have it enabled automatically as well, but will not perform well. So basically, yes, Truform comes enabled.
If you really meant smoothvision, all smoothvision is a algorithm for FSAA designed specifically for Radeon 8500 to get better performance/quality ratio. So with the R8500, you can enable smoothvision in any game as long as it's hardware accelerated either D3D or OpenGL. So to more accurately answer your topic, no, you dont have to buy a special half life for smoothvision (or Truform), it's included in either drivers or patches.