Yes (though unlike traditional third party intermediaries, there is no third party custodian for money you receive, meaning you don't have to trust 21 to not steal/freeze funds you've received). The innovative component of this that Bitcoin brings to the table is that the payment system linking the users to the developers is open/non-proprietary, with no registration walls encumbering usage.

I don't know how 21 actually works but it could be built in a way that the example code on their home page works without ever talking to their servers. That could code manage the transaction directly with the block chain.

Similar to the internet and AOL in the late 90's..