What: Shares of SunEdison Inc (NASDAQOTH:SUNEQ) jumped as much as 14% in early trading Wednesday after hedge fund manager David Einhorn got a seat on the board of directors.

So what: SunEdison has appointed Claire Gogel, a former partner at Einhorn's Greenlight Capital, to be an independent director. The company also agreed that for two years the company wouldn't issue any new equity without a supermajority vote of the board of directors.  

Now what: What investors are really cheering today is David Einhorn's increased involvement in SunEdison, a company he has about a 6.8% stake in. He could provide some valuable credibility to the company with other investors.  

I'll point out that hedge funds' dealings with SunEdison have been a double-edged sword. It was Altai Capital that prodded for change in 2013 that created the SunEdison we know today. And Einhorn's Greenlight Capital has been long the stock all the way from the peak to the bottom. There's no guarantee he will be the company's savior, although traders today like that he's taking a more active stake and limiting potential dilution.