Well, now you can do it!
Wizards has released the d20 System Reference Document under the Open Gaming License. More info can be found here:
http://www.wizards.com/D20/article.asp?x=srd
And here (for the OGL):
http://www.opengamingfoundation.org/index.html
Oh, just be sure you get permission from Paramount first! Then again, don't use trademarked names and such (i.e. call 'em Spacefleet instead of that other word) and you'll be fine! *
Steve
*This does not constitute legal advice and is presented in a purely humorous manner.