Technology

This is actually addressed as well. The initiative doesn't oblige currently developed or already released games to have such features, as it recognizes all the financial/legal complications that may arise. It only concerns future games, and refers to the experience of many old games being initially designed with player servers in mind, rendering it possible to play them even now.

It is absolutely possible and normal to do this, and it's really only the recent practice to act otherwise, which is why Stop Killing Games arose just now.

That being said, of course this decision would affect the developer's bottom line. First, as another commenter mentioned, they won't be able to push new games so aggressiely if players can stick to the old one, forcing them to focus on quality and originality of content, which are both more expensive. Second, publishing server code renders them unable to break licenses and steal server code, forcing to make in-house solutions or compromise with open-source. This is, by the way, why Microsoft only now opened the code of MS-DOS - it waited until all the potential lawsuits on IP infringement are expired.

Stop Killing Games will force more transparency, and developers hate that, because they don't want to admit they manipulated players and broke the law to get here. But they should never have done either in the first place.