Warren Buffett, start-up investor? Of course not. But the Oracle of Omaha still exerts influence over the entrepreneurial realm in some unexpected ways, both on paper and in spirit.

Buffett, the CEO of Berkshire Hathaway (BRK.A) (BRK.B) , "has never allocated capital to a start-up and wouldn't, because he's way too conservative," said Lawrence Cunningham, corporate law professor at George Washington University and author of Berkshire After Buffett. "On the other hand, the operating companies are allowed to do whatever they want pretty much."

Those companies include a variety of household names, from fast-food chain Dairy Queen to auto-insurer Geico and Burlington Northern railroad. And some of them, like furniture business CORT, are dipping their toes into the start-up realm. So are companies in which Buffett has simply amassed a stake, rather than making an acquisition outright.

Berkshire investment Munich Re, an international reinsurance group headquartered in Germany, is backing a start-up accelerator, for example. Its Spanish division has partnered with Madrid and London-based venture capital firm Mundi Ventures to put together MundiLab, a year-long program meant to boost digital companies in the insurance and reinsurance industries.

"Munich Re wants to position themselves as an innovation leader," said Leire Mancisidor, investment director at Mundi Ventures. "This is sort of a tool that they use to enable not only themselves but also their major leaders and major customers to come full speed when it comes to disruption, innovation in business and industry and trying to adopt new processes, and integrate with start-ups doing new things."

Some of that interest may be driven by challenges in the reinsurance business, where increasing competition has curbed profitability, a trend Buffett himself has pointed out. 

"One element of our strategy is based on our ability to innovate, particularly in these times of extreme competition in the traditional reinsurance business," Munich Re chairman Nikolaus von Bomhard said at the company's annual meeting. "Innovations enable us to keep pushing back the boundaries of insurability and to tap into new markets."

Berkshire amassed a major stake in Munich Re in 2010, and owned 11.8% of the company as of the end of 2014. He trimmed the investment this year to 9.7%, Munich Re said in a statement in September.

Munich Re isn't the only of Buffett's picks catering to the start-up crowd.

CORT, a furniture rental company Berkshire bought in 2000, said many of its clients are budding companies. Part of Berkshire's financial products division, CORT brought in $36 million in earnings in 2014.

"We do a lot of business with start-ups as they are starting to start their business and often times, when they're just starting out, they're not sure that they want to invest their capital in office furnishings, especially if they're not sure what the end game is going to look like," said Paula Newell, vice president of strategic business development at CORT.

Some of Berkshire's former executives have also demonstrated entrepreneurial leanings -- namely, those involved in its private aviation company NetJets.

Jordan Hansell, the former NetJets CEO who resigned in the midst of a contract dispute with the firm's pilots union, made a jump to the start-up world, joining Ohio-based digital insurance agency QuickInsured in June. Richard Santulli, the company's founder who resigned as CEO in 2009, started Milestone Aviation, a helicopter leasing company.

But running a Berkshire company itself requires a spirit of entrepreneurship, as Buffett prefers to keep a rather loose grip on the reins.

"Buffett gives almost 100% autonomy to the managers of each of their businesses that they own," said David Kass, a professor of finance at the Robert H. Smith School of Business at the University of Maryland and author of a blog dedicated to Berkshire Hathaway. "Within that context, each CEO, so to speak, of each business has the freedom to pursue entrepreneurial opportunities, expanding into new areas or related areas." 

And thanks to Berkshire's backing, its managers have access to something most entrepreneurs don't: tax-free money.

"Buffett's principal role as CEO of Berkshire is to allocate capital," Kass said. "He allocates capital that's being generated by one of his companies and allocates it to another of his companies where he perceives there are the greatest opportunities for growth or the highest expected return on capital. So, what's unique to Berkshire is you have a tax-free environment in the sense that you don't have to pay a capital gains tax on profits coming out of one company before you reinvest it in another."

To be sure, Buffett won't likely be investing in Uber or any other unicorns anytime soon. Cunningham emphasized that Buffett's start-up involvement happens "only indirectly and down at the lower levels."

When it comes to his own portfolio, the billionaire is famously technology-averse.

At Berkshire's 1999 annual shareholders meeting, he acknowledged that new technology is "very beneficial" from a societal standpoint but as an investment, isn't his cup of tea. "Our own emphasis is on trying to find businesses that are predictable in a general way as to where they'll be in 10 or 15 or 20 years," he said. "That means we look for businesses that in general aren't going to be susceptible to very much change."

But Buffett has evolved somewhat. To those traveling to Omaha, Nebraska, for Berkshire's annual meeting this year, the Oracle recommended finding a place to stay via online accommodations platform Airbnb.

"Airbnb's services may be especially helpful to shareholders who expect to spend only a single night in Omaha and are aware that last year, a few hotels required guests to pay for a minimum of three nights," he wrote in his 2014 letter to investors. "That gets expensive. Those people on a tight budget should check the Airbnb website."