Some jurisdictions ban betting, others ban facilitating betting (e.g., running a betting site). If your jurisdiction bans the act of placing a bet then it would likely be illegal for you to use Augur within your jurisdiction. If, on the other hand, your jurisdiction only has a ban on the facilitation of betting, then the Augur platform may be illegal (though, its unclear who the criminal here is since Augur is a decentralized platform), but its usage may be legal.
As with most laws, those revolving around gambling have not kept up with changing technology and therefore are up to massive speculative interpretation until tried in court. If you are concerned and live in a jurisdiction that limits your personal freedoms, the safest course of action is to either consult an attorney (who will probably tell you the answer is unknown) or simply don't risk it.