I actually really like the developer's rationale for why they use an anime character as the mascot.

The whole blog post is worth reading, but the TL;DR is this:

Of course, nothing is stopping you from forking the software to replace the art assets. Instead of doing that, I would rather you support the project and purchase a license for the commercial variant of Anubis named BotStopper. Doing this will make sure that the project is sustainable and that I don't burn myself out to a crisp in the process of keeping small internet websites open to the public.

At some level, I use the presence of the Anubis mascot as a "shopping cart test". If you either pay me for the unbranded version or leave the character intact, I'm going to take any bug reports more seriously. It's a positive sign that you are willing to invest in the project's success and help make sure that people developing vital infrastructure are not neglected.