We are still talking to the lawyers but my rough draft is
"You may use Raspberry Pi trademarks and logo
a. The Raspberry Pi word mark is not part of the product
name, company name or website URL.
b. The Raspberry Pi word mark is used in a referential
phrase such as “runs on,” “for use with,” “for,” or “compatible with.”
c. The Raspberry Pi word mark appears less prominent than
your product name.
d. The product is in fact compatible with, or otherwise
works with, the referenced Raspberry Pi product.
e. The reference to Raspberry Pi does not create a sense
of endorsement, sponsorship, or false association with Raspberry Pi or
Raspberry Pi products or services.
f. The use does not show Raspberry Pi or its products in
a false or derogatory light.
g. If the logo is used on a website it links to http://raspberrypi.org
h. You use the acknowledgement "Raspberry Pi is a
trademark of the Raspberry Pi Foundation"
i. You may not manufacture, sell or give-away merchandise
items, such as T-shirts and mugs, bearing Raspberry Pi trademark, including
symbols, logos, or icons, except pursuant to an express written trademark
license from Raspberry Pi."