Tumblr CEO David Karp stopped by the Colbert Report last night, where he talked Tumblr’s future profitability, porn on the site, and why he dropped out of high school at the age of 15.

Early on in the interview, Colbert implies that Karp is “successful” with his Tumblr venture, to which Karp replies:

“Not yet. I’ve got lots to prove. We gotta get this thing to profitability first – that’s a pretty big milestone.”

Since the Yahoo acquisition, Tumblr has already implemented more ads. The previously staunchly anti-ad Karp recently embraced the idea of ads on the network, saying that he hoped advertisers would win Lions awards for their future work on Tumblr.

Addressing the porn issue, which was a big point of contention when Yahoo first announced their Tumblr acquisition (users though that the deal meant censorship was on the way), Karp shied away from the “porn central” label. But he did indicate that they weren’t interested in limiting that type of content.

“Look, we’ve taken a pretty hard line on freedom of speech, supporting our users’ creation – whatever that looks like,” said Karp. “It’s just not something that we want to police.”

Yahoo CEO Marissa Mayer has echoed those sentiments, recently saying that they won’t work to restrict porn, as it’s “the nature of user-generated content.”

Check out the full interview below: