Internet auction giant eBay has acquired Critical Path Software, the app development company that helped it launch key applications for the iPhone, its ticket reselling business and its online classifieds service.

Terms of the deal were not announced. The companies have worked together for more than two years on apps like eBay for iPhone, StubHub, eBay Classifieds and shopping.com.

“We’re very serious about innovating in mobile commerce, and this acquisition underscores our commitment to bringing the very best and brightest in the field to eBay,” said eBay Marketplaces chief technology officer Mark Carges in a statement.

The acquisition of Portland, Ore.-based Critical Path will help eBay expand its presence in the mobile commerce market. The companies most recently collaborated on eBay’s iPhone 2.0 core app, which has been downloaded more than 14 million times since its launch in 2008.

Last year, the value of all goods sold through eBay’s mobile unit was more than $600 million. The company expects the unit to generate $1.5 billion in gross merchandise volume by the end of this year.