There isn't one. The only difference is who's ego you stroke ESR(Open Source), or RMS(Free Software).
From the history of the OSI:
The conferees decided it was time to dump the moralizing and confrontational attitude that had been associated with "free software" in the past and sell the idea strictly on the same pragmatic, business-case grounds that had motivated Netscape.
From the history of the OSI:
The conferees decided it was time to dump the moralizing and confrontational attitude that had been associated with "free software" in the past and sell the idea strictly on the same pragmatic, business-case grounds that had motivated Netscape.
The only difference is marketing not substance.