KanjiVG website (https://kanjivg.tagaini.net/
) points to this license,
I'm no expert in this matter, but it would seem to me that you could indeed use this project for your own commercial product(s). BUT
1) You must credit the author (see "Atttribution)", link to the original work, etc. Basic courtesy stuff IMHO.
2) Your commercial product is then bound by the same license (see "ShareAlike"), so a third party would be able to take your product, modify it, and resell it OR give it away for free without asking your permission or paying you any money (just giving you "credit" for your work in the form of an acknowledgement, as per above), as long as this third party's product is offered under the same license.
Thus, I would assume that you are supposed to make your source code freely available so that it can be reused by other developers.
Again, that's just my understanding. If anyone else knows more and wants to add, clarify or correct any points, please post a new comment.