Are KickStarter and IndieGogo incompatible?

Is there anything stopping me from posting my project on both crowdfunding sites KickStarter and IndieGogo? My rationale for doing so would be that I would expose myself to more people.

Are there licensing issues or other reasons for posting my project to only one crowdfunding site?

Not quite sure what you mean by incompatible. They have different models. Good thread on Quora discussing the effectiveness of each.

As for running campaigns on both platforms at the same time: not a good idea. From someone who tried:

having two campaigns running simultaneously on two separate platforms was diluting the message to the point where both suffered.

There's nothing in either of their terms that limits you from doing so.
In fact, Indiegogo's terms indirectly suggest Project Entities are "free to solicit other funding for the Project".

http://www.indiegogo.com/about/terms Whether sourcing funding from both sites is a good idea for your particular project is another question...