Yes, to first connect to someone you share a qr code with them or send them a link. The medium in which you share the link does not have to be secure, it is only to make the first connection between the two of you.
Here's a high-level overview explaining how it is possible that there are no user identifiers.
Basically, with each contact you agree on different servers which relay your messages. You get separate communication tunnels for every contact. And these tunnels can be replaced by other tunnels at any time.
It tries its best to be user friendly tho, that's a main concern of the dev. You should hear him talk in the main support group, he's really good.
You can also connect to the dev directly to express any concerns or ask questions. He will actually listen to you and shift his focus if multiple people tell him the same thing.
However, the software is only a few years old (much younger than all the other established messengers) and may not be ready for public use yet, but surely in the future.
Unlike P2P, messenges are sent over easily replacable relay servers so both parties don't have to be online at the same time to exchange messenges.
SimpleX is special because it is the only messenger that has no permanent user identifiers whatsoever. Not even a randomly generated string of characters and numbers.
This implies a LOT more privacy and security, especially for metadata-protection.
The server of Signal for example can't read your messages, but they know who sent how many messages at what time to which people. They know your entire graph of social connections. SimpleX does not.
Who argues about copyleft and libre? The FSF and Stallman are clear about libre meaning the same as free.
MIT is just as free/libre as GPL, but copyleft is the logical choice when you value user freedom.