Software development studio Tapbots is no stranger to the iOS ecosystem, with an entire stable of "bots" available on iPhone and iPad to do your bidding. Their headliner app is Tweetbot, a Twitter application with lots of features absent from the official iOS Twitter client.

Tweetbot is popular, and creating a desktop version is the logical next step. The official OS X Twitter app is a sad and long-neglected thing, built from the ashes of the once-great third-party app Tweetie. Tweetbot for OS X, on the other hand, brings with it all of the extra features of its iOS cousin. When it was announced it seemed that it would be welcomed with open arms by Twitter-using OS X folks everywhere.

But nothing is ever that simple in Twitterland. Back in August, Twitter announced a potentially crippling set of changes to the upcoming 1.1 version of their API, which third-party applications must use to interact with the Twitter service. Chief among those changes was a general prohibition against apps that "mimic or reproduce the mainstream Twitter consumer client experience." Twitter required that all preinstalled third-party Twitter apps be "certified" by Twitter, with the terms of that certification being unknown. There was also a limitation of 100,000 users per app, enforced by handing out per-user "tokens" for use with Twitter's OAuth authentication service. The 100k user limit is soft and can be negotiated, but ultimately leaves the number of users a third-party app is allowed to have in Twitter's hands.

Tweetbot for OS X was already in public alpha when the 1.1 API changes were announced. Tapbots reacted by pulling the alpha from their website, citing the token limit issue as being the main driving factor. A public alpha would quickly consume non-expiring tokens, which could severely limit the number of copies of Tweetbot that could later be sold.

Still, the app was very much anticipated by the OS X Twitter community. Its release announcement last Thursday was met with joy—and also a bit of puzzlement. Tweetbot for OS X launched at the unprecedented (for a Twitter client) price of $19.99. It's a bit difficult to swallow, especially when the official Twitter app is free. In fact, the $19.99 price makes Tweetbot for OS X the most expensive Twitter app available on the desktop. What gives?

Talking with robots

To get to the bottom of the pricing question, Ars reached out to the Tapbots themselves and spoke with Paul Haddad, one of the studio's two founding developers.

"I actually don't think we're competing with any free apps right now," he told us via e-mail. "Twitter for Mac has from all appearances been abandoned. Echofon for Mac has been officially discontinued. TweetDeck is targeting a totally different set of users and their app is more of a Web app than a Mac app." The price for the desktop app only seems high, he continued, because of the frantic "race to the bottom" on the iOS app store. "The original Tweetie for Mac was $19.95 (it was launched at $14.95)," he points out, and "if you look over the list of Top Grossing apps on the MAS it's very hard to find anything that's under $20."

The launch post on the Tapbots blog draws a direct link between the number of "tokens" a third-party desktop app is allowed to use and OS X Tweetbot's price. In order to send and receive tweets to the Twitter service, each copy of a third-party app must have a unique cryptographic identifier, or token, and Twitter has clamped down on the number of tokens being giving out. A token limitation is effectively a user limitation; worse, it's easy for users to consume multiple tokens by using multiple Twitter accounts.

The token rules are a sticky issue for the desktop Twitter app community, since it directly constrains sales of third-party apps. If sales are limited, the amount of money a third-party dev can make is commensurately limited. This affects the support they can give and removes the incentive to develop future apps. At first glance, it looks like each third-party app gets 100,000 tokens and then that's it, but the allocation guidelines are bit more complicated.

"There's a lot of confusion over this," said Paul. "The actual rule is any app that didn't have 100k tokens in use as of August 16, only gets 100k tokens. Any app that had over 100k tokens in use, gets twice their value. We had over 100k tokens in use for our Alpha at the time of the announcement." The Tapbots blog also points out the restrictions apply to the OS X version only: "The [desktop] app's limit is separate from, but much smaller than, the limit for Tweetbot for iOS."

A built-in upper limit means developers cannot be open-ended in their pricing—the app must be priced to make the required amount of money with the available number of copies to be sold. We asked Tapbots if they knew when they might actually run out, based on the first day's sales, but Paul said that it's too early to tell. "Sales were very nice, if you look we're the number two top paid and grossing in pretty much all the different countries' App Stores, just behind Mountain Lion. At this time we have no idea when we'll run out, we'll know better in a week or two once we can get some more data on how they are being used."

The obvious solution: simply ask Twitter for more tokens. But that doesn't appear to be possible. The guidelines don't make it clear how a developer can request more; there doesn't appear to be a formal request process, nor does it seem to be a matter of coughing up a check. "As far as I know there isn't [a method]," Paul replied to the question. "We've asked and made multiple suggestions," he said. So far Twitter remains mum on the issue.

Paul was polite and politic when we asked him about what his experience has been working with Twitter through the OS X Tweetbot development process. "Their developer relations group is very helpful and we work very closely with them. I will also say they haven't changed their guidance from the original August 16 post and I don't believe they will."

Despite the limitations, Tweetbot for OS X remains a priority for the Tapbots crew. "We plan to continue to develop and support Tweetbot on all platforms for as long as possible. We've been adding new features to the iOS version and have recently submitted a new build to the App Store. We'll also be submitting a new version for Mac fixing some bugs and adding a number of requested features."

It's difficult to view Twitter's API restrictions as anything other than a push toward monetization of the platform, something with which Twitter has traditionally struggled. Third-party apps might potentially circumvent promoted tweets or other paid types of content, or otherwise not show users the same things the official Twitter app does. "I can't read their minds," said Paul, when asked about Twitter's goals and what their eventual endgame strategy might be. "From what they said it sounds like they feel a consistent user experience is of paramount importance. We and many others disagree, unfortunately it's their network and they can do whatever they want."