Patrick Buchanan did not run as a Libertarian. He left the Republican Party and ran on the Reform Party ticket. (that was the legacy of Ross Perot's Presidential runs)

Ron Paul voted against amending the US Constitution to define marriage. http://clerk.house.gov/evs/2006/roll378.xml

I'm pretty sure he takes the position that it should be up to the states to decide that question.

I'd be surprised if Ron Paul ended up running as a Libertarian again. Well... okay, actually I can think of one reason --- automatic ballot access in additional states.

Steve