Thanks for sharing this.

Some remarks:

• The generator can be used offline, no need to be connected to the internet.
• It's open source, you can check the source code and compile it yourself.
• It can generate custom vanity addresses of any length (though longer than 6 characters will take a very long time)
• It's created by user pblck who's a well known coder, active user in the Waves Slack and he also created http://dev.pywaves.org
• The location of the source is: https://github.com/PyWaves/wallet-generator/releases

If you don't trust the generator, even after compiling it yourself an disconnecting your computer from the internet, you can always use the https://beta.wavesplatform.com website or any official Waves client to generate new accounts until you find one with the letters "B", "C" and "H" in it.
In my experience, 2 or 3 attempts is enough. Your Waves address may already contain those letters.

And it's not mandatory to participate in the airdrop, so don't feel obligated to do so.