Providing the source code is required even if the software is unmodified. Read §3 of GPL v2!
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www.gnu.org]
However, it's okay to provide links to the MySQL download site:
"If distribution of executable or object code is made by offering access to copy from a designated place, then offering equivalent access to copy the source code from the same place counts as distribution of the source code, even though third parties are not compelled to copy the source along with the object code."
(from GPL v2 §3)