[castell]

Bethesda introduced DLCs to the PC gaming world in 2006: http://en.wikipedia.org/wiki/The_Elder_Scrolls_IV:_Oblivion#...

  The first update came as a set of specialized armor for 
  Oblivion‍ '​s ridable horses; released on April 3, 2006. 
  Although gamers generally displayed enthusiasm for the 
  concept of micropayments for downloadable in-game content,
  many expressed their dissatisfaction at the price they 
  had to pay for the relatively minor horse-armor package 
  on the Internet and elsewhere.[85] Hines assured the 
  press that Bethesda was not going to respond rashly to 
  customer criticism.

Valve introduced DRM to the PC gaming world in late 2004: http://en.wikipedia.org/wiki/Steam_(software)#History

  Valve's Half-Life 2 was the first game to require 
  installation of the Steam client to play, even for retail 
  copies. This decision was met with concerns about 
  software ownership, software requirements, and issues 
  with overloaded servers demonstrated previously by the 
  Counter-Strike rollout. During this time users faced 
  multiple issues attempting to play the game.

There are alternatives like GoG, that are DRM/DLC-free.

[vacri]

Valve introduced DRM to the PC gaming world in late 2004

Utter nonsense. Have you never played an abandonware game from the late 80s and early 90s? "Enter the first letter of the third word on page 14 of the manual"? I used to get pirated Amiga 500 floppies with the copy protection stripped out and a little boot animation from the pirates inserted.

Valve introduced Steam to the PC gaming world... but then again, it's their product. And when all is said and done, Steam has been a significant net benefit.

[castell]

You are wrong. DRM != copy protection

You can own the DVD with a copy protection and even legally create a backup-copy. You simply cannot own a DRM product, as its bound to a server side check. DRM products may suddenly vanish from your PC, or change its content. Valve already wiped some games and changed the regional settings (removing games from certain parts of the world in retrospect) and Rockstar released an automatic patch for GTA San Andreas (2005) over Steam which altered the game (broke several features like widescreen support, removed several songs from radio stations)

[vacri]

Copy protection is a form of DRM. It is used to manage rights to digital content. You're redefining DRM to mean "the trend of selling licenses rather than software", which is only one form of DRM.

[castell]

It's the other way around! DRM is a specific form of copy protection. Read the DRM article on Wikipedia: http://en.wikipedia.org/wiki/Digital_rights_management

  "The term [DRM] is also sometimes referred to as copy 
  protection, copy prevention, and copy control, although 
  the correctness of doing so is disputed."

And read http://en.wikipedia.org/wiki/Copy_protection

[pearle]

Bioware was doing DLC before it was called DLC and long before Bethesda.

Google Neverwinter Nights premium modules.

[blakeyrat]

We used to call them "expansion packs". They were the same thing as DLC, just without the DL. (Nobody had enough bandwidth to do large game asset downloads.)

The concept's old as dirt.

[frik]

Expansion packs or Addons came with a lot more high quality content with many more hours of actual gameplay content on a separate CD/DVD. The CD/DVD can be sold later.

Since 2006, a DLC is usually a minor content like a horse decoration, a car, a few short missions worth 1-2 hours gameplay, etc. DLCs come also with DRM, you cannot sell it later. (Also used in conjunction as pre-order bonus on e.g. Amazon or Steam) (Some still release Addons, some call Addons DLCs, but generally it is the way as described above.)