OP_RETURN and non-standard transactions

I have an idea that uses OP_RETURN. However, the wiki states that "Note that this mechanism is not yet a standard transaction type, and thus will not be relayed by nodes on mainnet."

If it doesn't get relayed by nodes (and rather only included if you've mined that block), then how did this particular transaction get in there?

https://blockchain.info/tx/eb31ca1a4cbd97c2770983164d7560d2d03276ae1aee26f12d7c2c6424252f29

Also, I was wondering what is meant by this in the IsStandard() method?

Code:

// only one OP_RETURN txout is permitted
if (nDataOut > 1) {
reason = "mucho-data";
return false;
}

See here https://github.com/bitcoin/bitcoin/blob/master/src/main.cpp#L408-412