The whole plot of "returning presents that were taken" and it being free seems like it must be an apology. But if even half of the bad news going around is true, then its going to take much more to win back consumer good will. I just sincerely hope Pixel is doing well after the recent global events happening.

If anything it is a play on the fact that a mimiga named Santa appears in a section of Cave Story where you are rifling through fireplaces.

As far as the rumours are concerned, if it is the rumour about Nicalis stealing the Cave Story ip that is plastered all over the reviews section, then yeah, that's bullshit.

See here:
https://steamcommunity.com/app/1812280/discussions/0/3191360735171570825/

I don't make a habit of believing or spreading rumors but if you do some searching yourself you will see for yourself. Maybe some of it is blown out of the water, but credible gaming journalist sites have quoted him apologizing on Twitter for his behavior along with certain rumors. I just want to believe that hes genuinely trying to give back and make amends. (Though it will take more to win back any trust.)

About the IP thing, I think he owns the Cave Story Plus version while Pixel owns the unmodified IP. But with that its hard to find credible sources so don't take that as fact. That is what I believe to be true myself.