Everything we (&Olga) have ever published is henceforth dedicated to the public domain. In layman's terms, what this means is this: you are free to do anything you want with anything we have ever published (i.e. made publicly available, rather than shared via some private channel). There are no rules. You do not have to credit us (though you may, if you'd like). You do not have to provide any sort of "copyright notices" (in fact, please do not -- we do not posess the copyright to "our" works as a result of this dedication). You do not have to paste a LICENSE file into some folder, or provide our name in some "contributor list". Nothing. If you need a bunch of legalese, then:

• Our software can be considered to be under the UNLICENSE.
• Our software and our other works of art can be considered to be under CC0 1.0 Universal.

Please keep in mind, though, that these are worthless words written to protect us (and you) against worthless people. Nobody in their right mind should care about this mumbo-jumbo. Just do whatever you want with the stuff we made. A short FAQ follows, though you are free to skip this section.

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Q: Can I...
A: Yes. Q: Do I have to...
A: No. Q: What about earning money from your art?
A: We despise the very idea of that happening. We create for the joy of creation, and any chance at a material benefit creates a perverse incentive to alter our work in a way that causes it to "earn more" as opposed to just being better for the sake of being better. It also creates a feeling of "having to" do the work and a direct path to intense burnout. We do not want this, and we consciously opt to prevent it from happening (though there are plenty of public domain works that do earn money, but that's not relevant to us). Q: I found a work of yours that has a license (other than a public domain dedication). What gives?
A: Some works of ours have dependencies that they need to function. For example, if we make a game, it might depend on a game engine runtime to be playable. If we make a fork/patch/mod for someone else's work, it will depend on the base project. For cases like these, we try to outline as clearly as possible which parts are made by us (and therefore are public domain) and which parts are made by others (and therefore subject to their licensing terms).
To summarize: if you found such license terms, they do apply. Read them carefully and act based on the circumstances. Q: What use is that? If I can't take and use your full work, how does the public domain dedication matter?
A: You can try and replace the dependencies with less restrictive ones, or even author your own replacements, thus "liberating" the public-domain parts of our work from them. You can also change our work itself so that it no longer has those restrictive dependencies. Q: Why not include the waiver with every published work?
A: We try. However, it is sometimes impractical to do so.
Some publishing formats do not have a proper way to indicate licensing.
In some, adding a license causes side effects (for example: if you include an open license on GitHub to a project that relies on Jekyll, then Pages will add an ugly blob onto your site telling visitors to "contribute to the project", which is not what we want).
In some cases, the work has been created so long ago that going back to edit it is no longer practical: for example, it is published somewhere we no longer control.
In some cases we may have even forgotten it exists.
Generally speaking, if a work made by us lacks a license notice you can assume it's fully and completely placed into the public domain, unless you can identify an obvious bundled dependency. I cannot for the life of me think of anything that we wrote that would have those and not have a proper license, though. Q: What about future works?
A: The dedication holds for them. Q: Why do this at all?
A: Any form of license or contract is fundamentally a threat. It outlines artifically created "rights" and "responsibilities", and then says: if you don't follow through with the "responsibilities", your "rights" are forfeit. Depending on who you're dealing with, the implicit threat may be even worse: if you don't follow through with the responsibilities, we're going to sue you.
Unless you, as a publisher, intend to follow through with your threat, your license will not protect you, as it only stops good people from doing the stuff your license prohibits (those who wouldn't do anything you're not comfortable with in the first place).
And if you do intend to do so, you do plan to ruin someone's life over a piece of software, a game, a video or a drawing: you're an asshole.
We most certainly do not intend to follow through with any threats related to our works: we have neither the desire nor the means to do so, and we want our stuff to be shared, spread around, and used as a building block. Therefore, we will simply not make any threats at all. In their place, we shall offer one word: enjoy.