(Before DS acquired them in 1997, Solidworks had their own AutoCAD alternative, called "DWGEditor" and later renamed "2D Editor". DraftSight can be perceived as a direct competitor to 2D Editor, although Solidworks says that they'll keep selling both packages "for the time being.")
First of all, only the standalone license is free. That is, if you want to install it on a server and run it on multiple workstations on a network, you'll have to buy a network license. This is all spelled out in the end-user license agreement (EULA), which you really should read before buying or installing any software. The network license also includes telephone support and other goodies, though, so if you're a business it may be worth your while.