Your work is impressive to say the least! I have a copy of your free set of assets and wanted to first let you know I'm making a Minecraft modpack (NerdHaus-Adventures) that will feature many of the icons from the asset bundle. On the topic of licensing, the closest I plan on ever monetizing the pack is a donations page. I also am working on modifying some of the icons to fit the theme I'm going for.
Is this acceptable? I haven't published anything yet that uses the icons.