License compatibility is generally understood to refer to the problem of creating combined works out of code under different, clashing FLOSS licenses. Usually, it is seen as an issue only if at least one of the licenses in question is copyleft.

A surprising amount of intellectual energy among members of free software and free culture communities has been devoted to dealing with the issue of license compatibility. The same can be said of open source legal specialists associated with the more sophisticated corporate open source vendors, as well as companies in the business of selling tools and services to aid corporate management of open source. In general, incompatibility seems to be spoken of as a significant compliance issue. But critical analysis of the legal assumptions underlying received wisdom about license compatibility seems to be oddly absent. Moreover, and ironically, much of that received wisdom seems to bear little relation to actual conduct by free software developers.

This talk attempts to make some sense out of the topic of license compatibility, noting where it makes sense and where it seems to lack sufficient rational underpinning. I propose ways of adjusting how we think about copyleft license interpretation to place license compatibility doctrine on more solid ground and in line with the realities of free software development.