This is a free package! The content of this package includes 20+ flight magic icons that specially correspond to another visual FX package (“Flight Magic FX”) in the Asset Store. Although you might not need the FX, you can still download this icon package for single usage.
If a license is not included with an asset it’s automatically licensed under the Asset Store EULA. Check the second half of the document at the link below for that license. Short answer is that it’s permitted for commercial use.