Back in October, at New York Comic Con, Dark Horse announced an ambitious new digital comics program that would make many of their most popular titles available, at a discount, on a number of different platforms. At the time, they said the program would launch in January 2011 with about 150 titles.

Last week, Dark Horse posted an update on their digital comics page, saying that "factors beyond our control have impacted our plans."

While there could be many different reasons for the delay, recent developments suggest that Dark Horse's decision to allow readers to buy comics through their own digital storefront may have fallen afoul of Apple's prohibition on in-app purchases outside the iTunes store. UPDATE: Apple clarified today that this is not a new rule but simply stricter enforcement of existing policy. See below for more details.

At the Dark Horse NYCC panel last October, Micha Hershman said that readers would buy and download comics through the online digital bookstore and could read them on apps for the iPad, iPod, Android, and other platforms.

"The big news here is that it's a proprietary system," Hershman said. "We built it ourselves." He cited two chief reasons: "There is no censorship," he said. "We don't have to submit our comics to Apple for approval. The other reason is for creators: If we are not paying licensing fees to Apple, we can pay our comics guys more money."

Single issues of their comics would be priced at $1.49, Dark Horse promised, which also suggests that that the iTunes store is not involved, as Apple requires that e-book prices end in .99.

The problem is that Apple may not let them do it. The e-book site TeleRead reports that for the past few months, Apple has been rejecting magazine apps for its iPad that allow in-app purchases that don't go through the iTunes store. If that is what Dark Horse was planning—and it certainly sounds that way—then they may be hitting the same roadblock. Apparently Apple has been blocking new apps that aren't in compliance and have given developers of existing apps until June to follow the guidelines. The New York Times reported today that Apple rejected Sony's e-book app for precisely this reason.

When asked about this, Dark Horse spokesman Jim Gibbons said "No comment" and pointed to the statement on the Dark Horse website.

This could also spell big trouble for existing comics apps like comiXology, which support multiple platforms, allowing you to buy books through their web app and upload them to the iPad or iPhone. ComiXology CEO David Steinberger, contacted through his PR representative, responded, "Until Apple has an official statement, we don't have any official comment. We don't believe there is any issue."

UPDATE: Digital Daily reports that Apple does not prohibit all in-app purchases from outside sites, but it does require that developers offer the opportunity to make purchases through the iTunes store. This means that comiXology probably won't have an issue—but Dark Horse might.