When you have a device that has samples to play them, these come with a license to allow you to use the sounds as part of your own music. You can distribute your work without problems, but when you distribute the sounds themselves, you are basically go beyond what you are allowed to do, which is redistributing their work.
So legally speaking, you cannot redistribute those stand-alone sounds, free or as a paid download. If the vst is free, then you are still violating copyrights, although in that case they may not pursuit any copyright claims.
But its better to be on the safe side. Unless they ship a license file that explicitly states that you can do anything with it as you see fit, assume that you cannot.