Who Len was or what the blockchain is?

Len Sassaman was a very prominent member of the cypherpunk community who recently passed away.

The blockchain is the record of all transactions that the bitcoin network has processed. The blockchain is how bitcoin clients know who sent how many bitcoins and to whom.

I knew who Len Sassaman was. I did not know how the blockchain worked, or how Dan Kaminsky and Travis Goodspeed added this tribute to it.

Can you explain what Dan Kaminsky is trying to do with the Genesis block?

Edit: corrected for improper terminology. I understand now.

You are mixing two different terms here: The blockchain is a list of transactions that are linked to each other using cryptographic functions. Each block in the chain links to it's parent block. The genesis block is the first block created, it has no parent block. As proof that Bitcoin wasn't started before a specific date, the block references a The Times headline ("Chancellor on brink of second bailout for banks").

Dan Kaminsky figured out a way to embed ascii text into the block chain. I did not try to find out how he did it, but he probably created some transactions that include those strings. If you want to find out more about how he did it, he will give a talk at the Chaois Communications Camp related to Bitcoin.

I do not know what the genesis blockchain is.

(Presumably) Dan Kaminsky and Travis Goodspeed modified a bitcoin miner so that when it found a block, it would embed this tribute inside one of its unused field. (or rather, it embeds it in the transaction that is created as a part of generating a new block, the "coinbase".)