CDLA permissive compatibility

From OpenStreetMap Foundation

Kathleen Lu, September 2018


The LWG was recently asked to evaluate the CDLA Permissive 1.0 the CDLA is a relatively new data license under the stewardship of the Linux Foundation.

While we have not seen it used for new geodata sets yet, it may become popular, so it is important to consider its compatibility with ODbL. (For additional general understanding, an appendix identifies some key differences between ODbL, CDLA and other popular licenses like CC-BY.)

Analysis of CDLA and ODbL compatibility

After reviewing and discussing, we have concluded that CDLA Permissive is for the most part compatible with ODbL. (Note that this should not be confused with another license called CDLA Sharing, which is not compatible with ODbL).

CDLA Permissive is similar to other licenses in that its main requirement is attribution. Helpfully, with respect to identifying the license, it expressly contemplates "a hyperlink or other method reasonably likely to provide a copy of the text of this Agreement" as an attribution method. However, it also contains two clauses that are more ambiguous and confusing in the OSM context:

(b) You must cause any Data files containing Enhanced Data to carry prominent notices that You have changed those files;
(c) If You Publish Data You Receive, You must preserve all credit or attribution to the Data Provider(s). Such retained credit or attribution includes any of the following to the extent they exist in Data as You have Received it: legal notices or metadata; identification of the Data Provider(s); or hyperlinks to Data to the extent it is practical to do so.

Both these clauses appear to assume that the CDLA-licensed data will be the item shared, either with or without modification. These clauses do not appear to contemplate a scenario where the CDLA-license data is used to improve a much larger dataset like OSM.

It is unclear whether clause (b) would apply in the circumstance where the CDLA-license file is not modified. For an import into OSM, the geodata must be converted from whatever source into OSM's format, and then added, whether as one or several changesets, to OSM. The substance of the data is extracted and contributed, but the original "file" as that word is conventionally understood is left unchanged. (There is no definition of "file" in the CDLA).

As for clause (c), the CDLA does not state whether credit or attribution may be preserved by linking to a webpage with details (such as, nor does it seem to prohibit such a format. Given that the steward of this license is the Linux Foundation, it may be fair to consider common open source code license attribution formats as appropriate examples. Such notices are commonly found in links, text files that accompany code, headers or comments in code files, for metadata associated with packages of code. In comparison, OSM's copyright attribution page (which normally would include the identity of the source, a link to the open license, and a link to the data where available) seems in line with the first method. The question of metadata is a little harder. One can envision a CDLA-licensed dataset that includes metadata identifying a source for each individual piece of data. Such information could be difficult to carry over into OSM, a different database format. However, changeset comments (which should identify the source for all imports) possibly can be used to preserve attribution for specific data.


In sum, CDLA Permissive licensed dataset may be compatible with ODbL. However, one should be very careful in checking that all forms of attribution in a CDLA-licensed dataset can be preserved if importing into OSM's format.

If you are interested in adding data with an CDLA license to OpenStreetMap, please:

1) Double check that the dataset uses CDLA Permissive and not CDLA Sharealike,

2) Confirm that no additional terms have been added,

3) Review the data, data source, and any files that accompany the data for attribution files, statements, or other sourcing information or metadata. Preserving such information may require special attention and effort and it is your responsibility to ensure that such preservation will be carried out as part of an import.

4) Adhere to the general import guidelines, as with all imports.

Appendix: Key differences between CDLA, ODbL, and CC-BY

NOTE: There are two types of CDLA, CDLA Permissive 1.0 and Sharing 1.0. Creative Commons has Creative Commons Attribution (CC-BY) and Creative Commons Attribution-ShareAlike (CC-BY-SA), and each has multiple versions (the current version is 4.0, see When comparing, it is important to note the license type and the version as there are key differences (see CC-BY analysis blog Use of CC-BY data).

All of these licenses have attribution provisions, but CDLA Permissive and CC-BY do not have sharealike provisions. ODbL has a sharealike provision, but also the concept of "Collective Database" for which there is no sharealike obligation. CDLA Sharing and CC-BY-SA have more traditional "viral" sharealike provisions.

CDLA has a mutual defensive termination clause:

5.2 If You institute litigation against a Data Provider or anyone else who Receives the Data (including a cross-claim in a lawsuit) based on the Data, other than a claim asserting breach of this  Agreement, then any rights previously granted to You to Receive, Use and Publish Data under this Agreement will terminate as of the date such litigation is filed. 

This is similar to defensive patent termination clauses seen in many popular open source licenses, which were presumably the inspiration for this clause.

Unlike ODbL and CC-BY 4.0, CDLA Permissive does not have any type of DRM clause. CDLA Sharing does have a clause that a redistributor "may not restrict or deter the ability of anyone who Receives the Data (a) to Publish the Data in a publicly-accessible manner[.]"

Both types of CDLA expressly allow "Computational Use" of Data and do not restrict the publication of "Results" in anyway (including attribution).

Like CC-BY, CDLA Permissive expressly allows the material to be relicensed under a different license. ODbL allows for Produced Works to be under any license, but the Database and Derivative Databases must be under ODbL. CC-BY-SA and CDLA Sharing require any republication or redistribution to be under their respective licenses.