You can use any of the game system rules found in the Cortex Plus Hackers Guide. You are allowed to use the name “Margaret Weis Productions”; the name “Cortex Plus System” in your work.
You cannot create content for Firefly, Marvel Comics, Leverage or any other licensed setting at this time.
RPG supplements and settings only at this time. Short opening fiction to illustrate your RPG setting is allowed, but only if included in the setting material (not sold separately).
No artwork may be used from any Margaret Weis Productions publications. You may use artwork from DriveThruRPG’s Stock Art selection, public domain artwork. You must have permission to use any artwork.
Logos and Trade Dress
The Cortex Plus Community Created Content logo must appear on the cover of your work. It needs to be legible when viewed at full size. It does not need to and should not be the primary logo or title on your cover. You may not use any other logos or trade dress from Margaret Weis Productions publications.
You are encouraged, but not required to use the Cortex Plus Creator Template when creating your work.
You can find the template here.
The following text (must be placed within the Work, wherever the Work otherwise lists legal and copyright information):
This product was created under license. CORTEX PLUS and its logo, and CORTEX PLUS CREATOR STUDIO and its logo, are trademarks of Margaret Weis Productions in the U.S.A. and other countries.
This work contains material that is copyright Margaret Weis Productions and/or other authors. Such material is used with permission under the Community Content Agreement for Cortex Plus Creator Studio.
All other original material in this work is copyright  by [your legal name or company name] and published under the Community Content Agreement for Cortex Plus Creator Studio.
Neither your Work nor any promotional material, including blog posts or press releases, may contain racist, homophobic, discriminatory, or other repugnant views; overt political agendas or views; depictions or descriptions of criminal violence against children; rape or other acts of criminal perversion; or other obscene material without the express written permission of Margaret Weis Productions in a document separate from this License.
Illegal and Infringing content is not allowed. This includes material based on Firefly, Marvel Comics, Leverage, Dragonlance, and other settings owned by other companies. It is the content creator’s responsibility to ensure that their content does not violate laws, or copyright, trademark, privacy, or other rights.