1Licensing and contribution policy of dtc and libfdt 2=================================================== 3 4This dtc package contains two pieces of software: dtc itself, and 5libfdt which comprises the files in the libfdt/ subdirectory. These 6two pieces of software, although closely related, are quite distinct. 7dtc does not incorporate or rely on libfdt for its operation, nor vice 8versa. It is important that these two pieces of software have 9different license conditions. 10 11As SPDX license tags in each source file attest, dtc is licensed 12under the GNU GPL. The full text of the GPL can be found in the file 13entitled 'GPL' which should be included in this package. dtc code, 14therefore, may not be incorporated into works which do not have a GPL 15compatible license. 16 17libfdt, however, is GPL/BSD dual-licensed. That is, it may be used 18either under the terms of the GPL, or under the terms of the 2-clause 19BSD license (aka the ISC license). The full terms of that license can 20be found are in the file entitled 'BSD-2-Clause'. This is, in 21practice, equivalent to being BSD licensed, since the terms of the BSD 22license are strictly more permissive than the GPL. 23 24I made the decision to license libfdt in this way because I want to 25encourage widespread and correct usage of flattened device trees, 26including by proprietary or otherwise GPL-incompatible firmware or 27tools. Allowing libfdt to be used under the terms of the BSD license 28makes that it easier for vendors or authors of such software to do so. 29 30This does mean that libfdt code could be "stolen" - say, included in a 31proprietary fimware and extended without contributing those extensions 32back to the libfdt mainline. While I hope that doesn't happen, I 33believe the goal of allowing libfdt to be widely used is more 34important than avoiding that. libfdt is quite small, and hardly 35rocket science; so the incentive for such impolite behaviour is small, 36and the inconvenience caused thereby is not dire. 37 38Licenses such as the LGPL which would allow code to be used in non-GPL 39software, but also require contributions to be returned were 40considered. However, libfdt is designed to be used in firmwares and 41other environments with unusual technical constraints. It's difficult 42to anticipate all possible changes which might be needed to meld 43libfdt into such environments and so difficult to suitably word a 44license that puts the boundary between what is and isn't permitted in 45the intended place. Again, I judged encouraging widespread use of 46libfdt by keeping the license terms simple and familiar to be the more 47important goal. 48 49**IMPORTANT** It's intended that all of libfdt as released remain 50permissively licensed this way. Therefore only contributions which 51are released under these terms can be merged into the libfdt mainline. 52 53 54David Gibson <david@gibson.dropbear.id.au> 55(principal original author of dtc and libfdt) 562 November 2007 57