First off. USB or MIDI Interface, either one works for basic sequencing but for firmware upgrades and using the Roland Patch Editor the USB is the only way to go.
Also USB cable is a single cable as compared to two for an Interface.
The MIDI interface can still be useful for daisy chaining other MIDI hardware and can be used simultaneously with the Laptop USB interface.
Freeware DAWS are readily available for Windows machines these days.
Top of the line Cakewalk Sonar Platinum was bought out by http://bandlab.com
and is available for free download these days after you open an account with them.
There's also http://tracktion.com
For information on how to operate these programs simply go to youtube and search on (DAW NAME) tutorials
There are also freeware VST programs available. Google DAW and VST and you'll quickly learn what these programs are all about and how to use them.
Hope this helps,
The Juno DS is a terrific instrument and you should have lots of fun using it.