[rwjwjuwjudf]

The link you gave doesn't use the word implicit and actually says:

> Wherever possible, make sure you have an explicit license to any necessary patents held by the licensor.

Then it goes on to distinguish between weak and strong grants.

I think you mean weak, not implicit. AFAICT, there isn't an implicit grant with patent law, because the default is that you're infringing without an explicit grant.

[swhipple]

The link in the original post was about strong vs weak retaliation clauses in an explicit license, but the parent is also talking about implicit patent licenses, which do have some case law and opinions surrounding them in the United States [1].

The theory behind implicit patent licenses is that the licensee (often the buyer) will have some idea about which rights they have to the thing they are licensing, absent any other agreement. For a software license like the 3-clause BSD, this means that if they are licensing the software from the holder of the patent, they can reasonably expect to not subsequently be sued for infringing on the patent while following the terms of the license.

Omitting any kind of patent mention from your product's license, and later claiming infringement for reasonably expected use, would look subversive and generally be unconvincing.

[1] http://en.swpat.org/wiki/Implicit_patent_licence#USA