You are free to use BSD licensed code for anything, even commercial, closed source software.
How is that any different than just releasing it as public domain?
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The BSD licenses explicitly disclaims any warranty, which is not the case with public domain. For this reason alone, using the BSD license instead of releasing something as public domain is highly recommended.
In addition, some jurisdictions do not recognise the concept of releasing your work into the public domain, i.e. relinquishing your copyright!
Public Domain is region specific. From here:
There is no such thing as “putting a work in the public domain”, you America-centered, Commonwealth-biased individual. Public domain varies with the jurisdictions, and it is in some places debatable whether someone who has not been dead for the last seventy years is entitled to put his own work in the public domain.