Is he running for office? Yes
Are his views bordering extreme? No
Is he an independent? No
Is he running in the party he most agrees with? Yes
Is he actively campaigning? Yes, in fact he is working very hard to get into the debates because he is serious about the presidency.
I'm not sure how people are saying he isn't legitimate. He's more "legitimate" then Donald Trump in my opinion, if nothing else because he isn't manipulating the party system to get his votes.
He is legitimate as a candidate. Anyone that runs for president is technically a legitimate candidate. The mainstream media tends to try to tell people whether they are really qualified or not. Although I'm not voting for Johnson, I don't think he should be disqualified as not being a legitimate candidate.
Gary Johnson is the sitting Libertarian Party nominee for the current election, as he was for the 2012 election. Back then, he received just under 1% of the popular vote, which is a strong showing for a candidate of the Libertarian party. The truth is, though, we live in a two-party system. Gary Johnson does not have the funding or the bandwidth to come close to either Clinton or Trump. With so much distaste for both major party candidates, however, we will likely see a stronger showing than ever for someone like Johnson.
Gary Johnson enjoyed his time in the sun as a popular Libertarian candidate during an election that left many people unsatisfied with the two major party candidates. However, now that the election is nearing, more people are confirming their choices for President, choices that lie within the major parties and not with what Gary Johnson stands for.
Gary Johnson is not a legitimate third party candidate. Although he currently polls higher than most third party candidates, this is due to dissatisfaction with both major candidates. However, since he does not have a realistic chance to win, many people will end up voting for either Hillary Clinton or Donald Trump.