By Aidan Malley

Published: 01:05 PM EST

Although nearly all its business depends on a platform which launched just three weeks ago, Tapulous has become one of the most prominent iPhone and iPod touch developers with more than one million downloads in its pocket -- and attention that may turn it into one of the App Store's more serious players.

Speaking to TechCrunch, Tapulous chief Bart Decrem takes advantage of Apple's newly available access to download stats to estimate that his company will have one million downloads of the rhythm game Tap Tap Revenge before the weekend is over. The company is only the second to reach that tally after Facebook, which could rely on its large existing base of web users to achieve the record as well as support its development process.

The current version of the software is free, and so doesn't generate money by itself for the new developer. However, with an estimated five to six million iPhones and iPod touch players running the 2.0 firmware that supports Tap Tap Revenge, the download count would give about 20 percent of all up-to-date Apple touchscreen devices carrying some version of the software.

That high level of interest has drawn interest that may quickly turn it into a commercial force. According to Decrem, both indie and major artists are very willingly discussing a paid version of the game that would hold commercially available music rather than just the freely volunteered songs that make up the bulk of the music in the current version -- essentially following a licensing model like that of Guitar Hero or Rock Band, which most observers cite as Tap Tap's closest role models.

The surprising level of success appears to reinforce third-party studies that suggest at least some iPhone app developers are reaping significant rewards from the store. Few companies have publicly revealed how much profit they generate from paid or ad-supported software, but a Medialets estimate would have even a relatively small developer such as Pangea may have generated $1.2 million in opening weekend sales of its puzzle game Enigmo.

Such examples aren't universal; only a fraction of software at the App Store, free or paid, is likely to create that level of interest. Tapulous' own GPS-aware Twitter client Twinkle has only produced a far more modest 80,000 downloads, Decrem says, although it has been available for less time. Nonetheless, the appearance of multiple fast-rising apps is described as revealing a commercial potential for iPhone apps that wasn't evident before the App Store became available.