Apple’s Steve Jobs launched a rare open letter yesterday, panning Adobe Systems’s Flash video software as having “major technical drawbacks’’ and deepening a gap between the companies. Jobs said the decision to inn Flash from Apple’s devices stems from unease over the technology, not to prevent losing business.

This month, Apple launches new rules that force application developers to write programs unswervingly for the iPhone OS, rather than using mediator software such as Adobe’s products. That may have made Adobe less attractive to developers, a lot of of whom view Apple’s products as platforms they can’t disregard.

“It’s not a technology decision, it’s a business model: a closed, proprietary business model, with complete control, as different to having open advance drive what occurs across devices,’’ Narayen said at the time.

Adobe highlighted the risks of barring from Apple’s iPhone and iPad devices for the 1st time in a rigid filing this month, signaling ignore could damage sales.