Google uses Sqlite, which is simply public domain. Did someone at Google actually purchase one of their pseudo-license 'warranty of title' documents they offer for companies (supposedly mostly in other countries that officially don't recognize PD grants) with more legal budget than sense? Google also uses SBCL, which is mostly public domain "in jurisdictions where this is possible, or under the FreeBSD licence where not." Does the entry for it in the list of third party software say Google is using it under the FreeBSD license or PD? (They also employ at least one developer who is a core maintainer on the side.)
The legal department's default answer is "no" to anything they haven't already said "yes" to, so it wouldn't surprise me if your default options are limited. But presumably with useful enough software under other PD-equivalent things they could be forced to say "yes". As an aside I'd be very interested to know the extent of internal audits Google does on its code for legal risks in un-cleared-by-legal dependencies, dependencies-of-dependencies, and presence of code derived from stack overflow/popular books/random places on the internet indexed by google.
The legal department's default answer is "no" to anything they haven't already said "yes" to, so it wouldn't surprise me if your default options are limited. But presumably with useful enough software under other PD-equivalent things they could be forced to say "yes". As an aside I'd be very interested to know the extent of internal audits Google does on its code for legal risks in un-cleared-by-legal dependencies, dependencies-of-dependencies, and presence of code derived from stack overflow/popular books/random places on the internet indexed by google.