This file is the net layer API for the MySQL client/server protocol, which is a tightly coupled, proprietary protocol owned by MySQL AB. Any re-implementations of this protocol must also be under GPL, unless one has got an license from MySQL AB stating otherwise.
I am second to few in being a fan and a proponent of the GPL. However, this claim in this comment is utterly bogus. It dates back to willful misunderstanding and FUD spreading and the desire to strong-arm the sale of licenses on the part some people at the old MySQL AB company.
If license of source code followed network protocol of running implementation (which stretches "derived work" to an extent even an RIAA flack dare not even dream), then it would be illegal to view a web page served from IIS from Firefox.
And besides, the MySQL client server protocol is not even "owned" by MySQL AB. It's very directly merely extended (and not very much) from the old MSQL client server protocol.
To moot the entire issue, the new libdrizzle client protocol library not only speaks the new different and superior Drizzle client/server protocol, it also speaks the old MySQL protocol. The license for libdrizzle is BSD.
This whole thing makes me annoyed, because this kind of overreach and FUD just makes the GPL itself look bad.