EmojiTwo is a fork of the last fully free EmojiOne™ 2.x version.
The non-free EmojiOne 3.0 assets have been completely deleted. The EmojiOne project made changes to 2.2.7’s licensing. Previously EmojiOne did not require attribution for non-commercial and personal use (for proof see this snapshot of their website). Considering that the EmojiOne project ony changed the ReadMe file in that branch to mandate attribution in any case, EmojiTwo forked a state before those changes for greater flexibility.
Whether or not EmojiTwo will see continued development, is not clear. At the very least it serves as backup. Hopefully Free Software organsizations that adopted EmojiOne 2.x, such as Mozilla and KDE, will continue development of a fully free emoji set in some form.