The YouTuber who falsely insinuated Melania Trump's son was autistic is redefining chutzpah ... he's making money on his apology.

The guy has ads running on his apology vid, meaning he hasn't turned off the monetization setting -- just a one-click process.

The apology video posted Tuesday has almost 74,000 views as of Wednesday morning, and continues to run ads.

We broke the story ... Melania and Barron threatened the YouTuber with a lawsuit ... and they called out Rosie O'Donnell for reposting it.

The guy took it down when he felt the Mama Bear's legal heat -- although he waited 24 hours and gained another 1 million views, and more ad revenue, in the process.