Both Badlion and Moonsworth (Lunar client devs) are actual and reputable companies. BAC and Lunar aren't viruses, if you download them from the 'official' site (BAC / Lunar ) and not from a website hosted by my creepy neighbour. You're either lying or downloaded them from a weird site.

Is Lunar client a hack?

It is not a hacked client, it is bannable.

Can you get banned for using lunar client?

Nope, you can't get banned for using lunar.