I often get asked whether patterns found on RegexLib are free for use to
which my reply is...
They are free for use but, I'd recommend that, if you use one that you might
like to place a comment such as:
// pattern found at http://regexlib.com/AddressOfPattern
Reason is that, patterns get updated and also get comments left against them
so, it's a good way to leave useful info for another developer who may have to
maintain your code later!