Instead of the four letters, "DMCA", it might be better to use just three: "FBI". Specifically the FBI's anti-piracy warning seal and authorized language that explicitly informs the end-user of copyright law, and the authority of the FBI in such matters of law if under the appropriate jurisdictions.
One must keep one thing in mind, though: the FBI does not provide software licenses, and the DMCA isn't a license either, nor can either the FBI warning nor the DMCA be used as one.
However, you might then want/need to be clear about how this is handled in other countries, where - despite some extreme examples and often public opinion - US law does not apply or is simply not honored, or even conflicts with local law.
You might also wish to have an explicit document that cites relevant law and "reminds" anyone who reads it (and cares) about applicable law and the penalties for violating it.
However, attempting to craft a "license" should be done be a properly credentialed and experienced lawyer, for the same reason surgery is generally best left to surgeons - one small slip and it's all for naught. As a simple example, when the DMCA - or its interpretation and relevant case law changes - does your license become null and void, or at least unenforceable? Sever-ability, etc - all issues that require good counsel from someone who really knows their stuff.
Simply reminding people that it may be against the law - and you are granting no license otherwise - to reverse-engineer or distribute your code doesn't really require a lawyer, though one should be careful about the chilling effects of coming off as hostile to potential customers. A proper software license, custom written for your specifications, most certainly does.
