DayTrippers Open Source Rules version 3.0 - Creative Commons Release
The DayTrippers Source Rules have been updated to version 3.0. In addition to the PDF, the source document is also available in text-only format to facilitate reuse and derivation. These Source Rules are released under the Creative Commons Attribution 3.0 Unported License (Cc By 3.0)
This means you're free to do with it what you want, hacking it or adding to it, to create your own games. Like the commercial version of the DayTrippers CORE Rules, your derivative work may even be sold, as long as you note within the rules that it is based on the DayTrippers Source Rules.
The text version is right here.
The PDF version is PWYW at DrivethruRPG and RPGnow.
Now go forth and make some cool stuff!