I use MPro-7 as my 'primary' cleaner. Like the fact that there's no odor. I've found it to be very effective and have used it on shotguns, rifles, and handguns (including polymer frames). I'd recommend it based on my experience.
Uhh, I have been using M-Pro 7 since 1995 and have never had a "rust" problem directly due to the M-Pro 7 itself. It IS a strong degreaser so if you live in a humid area, you will have not corrosion resistance after using it without relubing your gun and could get surface rusting due to humidity.
I have left parts soaking in M-Pro 7 cleaner for days and never had any rust issues.
It may be water based but there is nothing to be worried about -- just use proper cleaning routines.