The online education company known as Coursera has racked up gaudy numbers within a year of its launch: 3.1 million users from around the world have signed up for an ever-expanding menu of courses offered for free from 62 leading colleges and universities.

On Friday, hundreds of educators from those schools gathered at the University of Pennsylvania to take stock of a movement that is transforming higher education. Some participants in the massive open online courses, known as MOOCs, wonder whether the phenomenon is oversold. Some said it is improving teaching on campus. And many marveled at the sudden global reach of their work.

James V. Green, a University of Maryland senior lecturer who taught one of the university’s first MOOCs this year, said the six-week course on developing innovative ideas for new companies drew 87,900 students, most from countries outside the United States.

“It’s a popular topic,” Green said of MOOCs. “We really do have an international audience.”

Kimbi Hagen, an assistant public health professor at Emory University, teaches a MOOC on AIDS that drew 18,000 students this year, including some from a village in Nigeria.

“It’s been a wild ride, really,” Hagen said. “It sounds corny. I wanted to make the world a better place. Emory is doing that in this course.”

Of Coursera, a start-up based in Mountain View, Calif., Hagen said: “I hope it comes up with a sustainable business model. I don’t want it to collapse.”

That question hangs over all MOOC providers, not only the for-profit Coursera, but also for-profit Udacity, nonprofit edX and others. Leaders of these enterprises face a challenge not unlike what media companies faced when they put free content online: how to convert heavy Web traffic to revenue.

Andrew Ng and Daphne Koller, the Stanford University computer scientists who founded Coursera, said the company is starting to bring in revenue from a trial program that offers special certificates to students who pay a modest fee, about $30 to $100, and take certain steps to verify their identity. The program, called “signature track,” has yielded $220,000 in 11 weeks, Ng said, and will expand. (U-Md. plans to participate.) Some of that money will be shared with universities.

The company is also exploring ways to raise revenue through proctored exams, for students who might want to obtain course credit, and through helping match employers with top students.

Ng announced Friday that Coursera will soon add an “app platform” to enable universities to add instructional tools, often interactive, to enhance their MOOCs. He said the company’s goal remains to promote a universal right to education.

“I want to live in a world where everyone has access to a great education,” Ng said. “I want to live in a world where people don’t have to choose between paying for tuition or paying for groceries.”

Idealism is tempered by questions about how to deliver great education online to the masses.

Molly Corbett Broad, president of the American Council on Education, an umbrella organization, said there is “profound skepticism” in some quarters of academia about MOOCs.

“A lot of folks in higher education think you guys in the press have hyped this,” she said. But she said MOOCs are likely to provide valuable data on what works and what doesn’t in online education, revealing how the average student learns. The council has recommended several Coursera MOOCs as credit-worthy, a key stamp of endorsement.

The forum showcased not only how MOOCs have reached students worldwide, but also how they are galvanizing a global network of online educators.

Margaret Sheil, provost of the University of Melbourne, which is offering MOOCs on macroeconomics, climate change and other topics, said the Australian university joined Coursera in part to extend its brand. Already, she said, Melbourne has a high share of international students. But publicity associated with Coursera, she said, has been “just phenomenal,” which could help enhance the university’s stature.

Wei Shyy, provost of the Hong Kong University of Science and Technology, which just launched a MOOC on science and technology in China, said a major attraction of joining Coursera is access to a huge trove of data on how students learn. But Shyy cautioned that there are limits to what a MOOC can accomplish.

“How do you do quality control?” he asked. “How do you do assessments? How do you work with students to add value? That, to me, is very challenging.”