Sure, but you have to include a link to Icons8 in your work. Free assets have limitations such as smaller sizes, select file types, or formats.
What's the difference between Pichon and Icons8 web version
They both use the same asset collections. But Pichon as a desktop app is much easier to integrate into your workflow — you can just drag and drop assets everywhere. Also, you can use it as a personal cloud for your own assets.
What benefits does a subscription provide?
Any of icons/illustrations/photos Icons8 subscription opens you a high-res images and vector formats for corresponding assets type.