The Starter Edition has been updated

StarCraft II: Legacy of the Void is out, and with it, a few new modes, such as the full co-op portion and Archon Mode -- which allows two players to control one base. But if you aren't willing to take the plunge yet, the Starter Edition has been updated recently to account for the Void expansion. In essence, you can download the game for free and get all of the new units, but you can only play with friends.

As an added bonus due to the recent patch, co-op mode is available, with three of the six characters at your disposal. If you're interested in seeing how the game has changed over the years, give it a shot.

Starter Edition [Battle.net]