Hawaii billionaires Pierre and Pam Omidyar joined 40 of the world’s richest people in a pledge to donate at least half of their fortunes as part of a philanthropists’ pact announced yesterday.

The Giving Pledge was organized by Bill and Melinda Gates and Warren Buffett to recruit multibillionaires to commit the majority of their accumulated wealth to philanthropy in their lifetimes or after death. Billionaires named in the first batch of 40 signatories, made public yesterday, include New York Mayor Michael Bloomberg, filmmaker George Lucas and former eBay President Jeff Skoll.

The Giving Pledge was hatched in May at a secret meeting in New York City. According to Sarah Steven, a spokeswoman for the Omidyars’ philanthropic foundation, the couple did not attend the meeting but were in contact with the Gates Foundation.

"(The Omidyars) seemed like a natural couple to reach out to," Steven said.

The Omidyars have already contributed millions of dollars to support social welfare and environmental enrichment programs across the globe through the Omidyar Network, a charitable trust based in Redwood City, Calif., with projects in sub-Saharan Africa, India and Hawaii.

"They’re always looking for ways to contribute where there’s real need," Steven said.

Pierre Omidyar is the founder of web auction site eBay, which he launched out of his apartment in 1995. The Silicon Valley startup has since become a multibillion-dollar giant with localized websites in 30 different markets around the globe.

Last year, eBay Inc. posted $8.7 billion in profits, including revenue from subsidiaries like online money transfer service PayPal and event ticket trading site StubHub.

Although he no longer participates in the company’s day-to-day operations, Omidyar remains chairman at eBay and holds a large chunk of the company’s shares.

He became an overnight billionaire in 1998 when eBay went public. In March, Forbes Magazine named him the 148th richest person in the world with an estimated net worth of $5.2 billion.

In 2006, the Omidyar family — the couple and their three children — traded their 45,000-square-foot Las Vegas mansion for a 5,800-square-foot home in Kahala.

Pierre Omidyar, 42, was born in Paris and spent most of his childhood in Washington, D.C., but lived in Honolulu for two years as a teenager. He attended the eighth and ninth grades at Punahou School and now serves on the board of trustees along with AOL co-founder and Punahou alumnus Steve Case. Pam Omidyar grew up in Hawaii Kai and attended ‘Iolani School.

Since moving to Hawaii, Pierre and Pam Omidyar have committed millions of dollars to local nonprofits and socially responsible investment. They endowed the Hawaii Community Foundation’s $50 million Omidyar Ohana Fund, which will provide $6 million in social service grants and $6 million for a sustainable kindergarten-first grade campus at Punahou.

Last year, the Omidyars also founded the Ulupono Initiative, which combines strategic for-profit investment with nonprofit grants to promote renewable energy, food production and waste reduction in the islands.

Reuse Hawaii — a nonprofit demolition contractor that salvages building material from homes across Oahu — is one of a handful of organizations and businesses in the state that receives grant money from the initiative.

"(The Omidyars) show their commitment to the environment in Hawaii by funding endeavors that are committed to sustainability," said Reuse Hawaii Director Selina Tarantino. "With the economy as it is right now, we really need individuals and companies to step up."

Tarantino said the Omidyar Network approached Reuse Hawaii as a candidate for funding more than a year ago and kept a close eye on the organization’s operations and finances to ensure that the grant money went to good use.

"We were on their radar," Tarantino said. "They need to know that the organizations that they are giving to will be there from year to year. They had confidence in us and our model."

Although it is not immediately clear how the pledge will affect their philanthropic efforts in the islands, the Omidyar Network said it is committed to Hawaii.

"(The Omidyars) are really passionate about the community there," Steven said. "It’s their home and they love it."