I've been a Ccleaner user for many years. Today for the first time ever I got a pop-up (I hate pop-ups) saying "thanks for playing fair. The free version of Ccleaner is for private use only. If you are a commercial user you must use the paid version," or words to that effect. What on earth led the software to conclude that I am a business?!
It doesn't think you're a business, it's saying that if a user is running it in a business then it's against the license. Everyone gets the same pop-up with the same text. It should be noted that there's a general feeling against the pop-ups that matches yours.
Why this pop-up all of the sudden, why now?
Nobody likes pop-ups and it like in the past with many other software examples it's a great way to drive users away into using a competing product that doesn't yet annoy like that. Personally I think their setup routine could be the solution: 1) install as Free home users only, or 2) install as Pro business license.