Twitter has finally made it clear what third-party developers are and are not allowed to do with its data going forward. Twitter wants control over how people view and interact with tweets, and so it is forcing people behind apps and clients like Tweetbot and Echofon to abide by stricter rules if they want to keep their services running.

The crux of the announcement is this: if you use anything other than Twitter.com or Twitter’s official apps to do anything with Twitter, you might be affected. For the community to survive, Twitter needs a viable business model (despite the “truckload” of money it has in the bank), and it feels it needs a bit more control over the ecosystem to do that.

Let’s roll back a bit. Twitter offered third-party developers access to tweets and other data very early on. It launched its first API, a tool developers use to build apps based on existing platforms, in September 2006. Developers used this to create their own clients, where you could read and post tweets instead of having to go to the Twitter website.

These clients played a big role in Twitter’s growth, as developers started creating their own businesses based on Twitter’s data and API access to the community. Twitter didn’t really have its own clients outside of its website until it bought Tweetie in 2010 and turned into its own iPhone app. People wanted to access Twitter in ways other than the website, whether it was on their phones or computer desktop, or even while playing World of Warcraft. That holds as true now as it did then.

Twitter’s now squeezing its API and exerting much more control over what developers can and cannot do with it. Let’s be clear that Twitter is allowed to do whatever it wants within the confines of the law. It’s the manner in which it has shut up shop which has irked the community.

Twitter wants you to have a “consistent experience” whenever you see and interact with tweets. That’s why it’s forcing apps and clients to abide by requirements for displaying tweets, otherwise they might have their API access shut down. New clients which use the “home timeline, account settings or direct messages” can grow to a maximum of 100,000 users (with one “user token” for each), while existing ones with more than that number using them will be able to double their existing userbase. Twitter can choose to give clients who reach the limits more user tokens if it wishes.

Developers have six months to make their apps compliant with the new rules after the API’s launched in a few weeks.

Twitter has an incentive to restrict the way third-party clients display tweets,  because the company's revenue model depends on displaying ads—something that not all third-party clients are set up to do. Certain features of clients, like hiding tweets with certain terms, don’t allow for that, and other clients just don’t display Promoted Tweets at all.

One of the big reasons why people are angry about the change is that Twitter has, over the years, spoken of the importance of third-party apps and clients. Cofounder Evan Williams (who was CEO at the time) wrote in 2010 that “third-party clients continue to play an important role for many people.” A few months before he replaced Williams as the head honcho, then-Chief Operating Officer Dick Costolo wrote:

We also provide a complete API into the functions of the network so that others may create access points. We manage the integrity and relevance of the content in the network in the form of the timeline and we will continue to spend a great deal of time and money fostering user delight and satisfaction.

In his announcement post, Michael Sippey, Twitter’s director of consumer product, included a chart showing the types of apps that are out there:

Twitter’s discouraging developers from creating apps that fall within the top-right quadrant. It mentioned Storify (which responded Thursday evening) and Favstar.fm, along with clients Tweetbot and Echofon. Services like the former pair are fine (though will have to abide by the new rules), Twitter suggested, though it’s been advising developers not to build clients over the last year and a half.

Third-party clients are likely to stick around, at least for a while. If you’ve paid to use your favorite client, you should still be able to use it as long as the developer is willing to support it and meet Twitter’s new requirements. However, Twitter is allowed to shift the goalposts at any time.

There are some other features and services which may disappear. Things like finding which of your friends are using another service might vanish, as we’ve seen with the Instagram incident. Instapaper founder Marco Arment is bullish about whether he is going to comply to keep the Twitter-based Liked By Friends browsing feature in his popular reading app. Arment pointed out that the demands to display tweets in a certain way is perhaps what led to LinkedIn losing tweet integration and Flipboard’s Mike McCue leaving Twitter’s board.

It seems Twitter is going the opposite route from Instagram. Where Twitter started with an open ecosystem and has moved slowly to take more control over the community and its data, Instagram started as an iPhone app and gradually became more open.

Nova Spivack (a cofounder of the Daily Dot), meanwhile, laid out the ways in which Twitter can generate revenue without having to clamp down on the API.

Looking at the positive side of this for a minute, some developers admit the changes aren’t all that bad, with the team behind Tweetbot saying it won’t run out of spaces for users for a few years. Even then, Twitter may grant Tweetbot permission to keep growing. The MetroTwit team is “cautiously optimistic.”

Secondly, the move should cut down on the number of poor quality or “spammy apps,” as well-known blogger and entrepreneur Anil Dash pointed out in a post highlighting the positives.

Maybe the mix of confusion, anger, and bemusement is why Twitter’s hiring a Platform Relations Manager to work closely with developers.

So where next? Sippey suggested that developers will soon have access to Twitter’s Cards technology. That’s the code that powers expanded tweets where you can watch YouTube videos, get previews of news stories, and view photos without having to click away from a specific tweet or your timeline. That’ll open the way for wider distribution of branded content—and, crucially, ads—helping Twitter become a more sustainable business.

There’s one point that really stands out for me amid all this. Twitter’s gone on the record as saying that it doesn’t want tweets appearing in a timeline “with non-Twitter content. e.g. comments, updates from other networks.” I have to wonder how that affects TweetDeck, which displays Facebook updates alongside tweets in a unified timeline.

Oh, yeah, it’s owned by Twitter.

It’s a far, far cry from the days when Twitter would share details of third-party clients on its blog.

Photo by RBerteig/Flickr