Blizzard Asserts Rights Over Independent Add-Ons

Blizzard has announced a policy change regarding add-ons for the popular game World of Warcraft which asserts requirements on UI programmers, such as disallowing charging for the program, obfuscation, or soliciting donations. Add-ons are voluntarily-installed UI programs that add functionality to the game, programmed in Lua, which can do various tasks that hook into the WoW engine. The new policy has some obvious requirements, such as not loading the servers or spamming users, and it looks like an attempt to make things more accessible and free for the end user. But unlike FOSS, it adds other requirements that assert control over these independently coded programs, such as distribution and fees. Blizzard can already control the ultimate functionality of add-ons by changing the hooks into the WoW engine. They have exercised this ability in the past, e.g. to disable add-ons that automate movement and facilitate 'one-button' combat. Should they be able to make demands on independent programmers' copyrighted works, such as forbidding download fees or advertising, when those programmers are not under contract to code for Blizzard? Is this like Microsoft asserting control over what programmers may code for Windows?

http://games.slashdot.org/games/09/03/21/148222.shtml