A rumor we reported on yesterday about eBay's open-platform plans exploded this morning on the blogosphere. Reporter Juan Carlos Perez of IDG had the most complete information in this article, including PayPal's plans to launch a new Developer Central portal to help developers create applications for PayPal.

eBay's plans to open the platform a la Facebook are apparently limited to Selling Manager. Developers we spoke to believe that this will help them reach more sellers. Currently eBay has a directory of third-party tools that it keeps squirreled away on its site, with little chance of users stumbling across it.

eBay's change in attitude towards its developers reflects its changing status from Wall Street darling with unheard of growth to a company struggling to keep its users engaged (or "delighted"). The shift is dramatic considering eBay's early treatment of developers, who had to pay eBay to be in the program. ChannelAdvisor had paid eBay well over $50,000/month in API fees before eBay eliminated most of the fees in 2005.

Perez said PayPal has 35,000 active developers, eBay program has 70,000 developers. Some of them are gathered in Chicago today as eBay's 3-day Developers Conference begins. A press release about the opening of Selling Manager, aka Project Echo, will be available soon and we'll cover in today's AuctionBytes Newsflash.

Update: Here's the news, and be sure to scroll to the bottom for speculation on further announcements.