My question is this, is dynamic VPN supported by Juniper today?
Short answer is Yes.
would I be able to deploy it as described in the article below, is this document still valid?
Yup, only caveat is that in some of the newer versions of JunOS the Pulse Client isn't hosted on the SRX anymore. I would advise you to use JunOS version 12.1X46-D35 ( the version after that has a bug ).
My understanding is that SRX comes with 2 dynamic VPN client licenses, is there anything else required ?
If you aren't planning on using more than 2 concurrent users on the device then no ( you can purchase more licenses for more than 2 concurrent users ). You should also keep in mind that Juniper sold the Junos Pulse Portfolio to another company ( Pulse Secure ), so in the future you will have to download newer versions of the JunOS Pulse Client ( Pulse Secure Desktop Client ) from their website or search for it online.