[License-review] estoppel explained

[Bruce Perens]

On 02/20/2012 09:00 AM, Carl Boettiger wrote:
> I believe some have also argued that [patent] is in fact not out of scope of MIT&  BSD. Is this true?
There is a doctrine in law known as equitable estoppel. Equitable means 
"having the quality of fairness", and estoppel means "stop".

Consider that Alice licenses software to Bob, using a simple license 
like MIT or BSD. Bob then uses the software, believing that he has 
Alice's permission to do so. Alice then sues Bob for infringement of her 
patent claims which are exercised in the same software.

Under the doctrine of equitable estoppel, Alice is stopped from 
prosecuting such a claim against Bob. Bob's action of using the software 
was carried out /with Alice's permission/ (we use the technical word 
"acquiescence" for this permission), and thus she is stopped from 
prosecuting an action that she permitted.

This is generally held to apply to licenses simple like BSD or MIT. 
Various licenses are worded to prevent an estoppel, but not those two.

My point is that abandonment of copyright doesn't equal permission to 
use, so we might not have this estoppel in the case of a simple 
dedication to the public domain.

Many jurisdictions (I think including the U.S.) don't have law 
affirmatively supporting one's right to voluntarily dedicate their work 
to the public domain. We have little case law to tell us how courts have 
handled this issue previously. So, we don't really know if a court would 
see that such a dedication implies an estoppel of any kind.

Larry Rosen is correct in pointing out that the doctrine of equitable 
estoppel might not apply in all jurisdictions. It also might not apply 
to all subject matter, such as patents, in jurisdictions where it is 
used. However, the United States is one where it has substantial history 
of successful use in cases.

Were CC to add specific language, it would probably apply across more 
jurisdictions than any implication.

John Cowan (I think) also made the argument that "use" is a legal term 
related to patents rather than copyrights, and thus the MIT and BSD 
licenses must /mean /patents when they say "use". However, I see the 
word "utilize", specifically regarding software, in U.S. copyright law 
{17 USC 117(a)(1)}, so it's unclear if John's argument would win.

     Thanks

     Bruce
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