Like the GPL, it requires that modifications to the software be distributed under the CeCILL, but it makes no claim to work that executes in "separate address spaces", which may be licensed under terms of the licensee's choice.

The disclaimers of warranty and liability are written in a manner different from other common open-source licenses to comply with French law.

[1] The CeCILL does not preclude the licensor from offering a warranty or technical support for its software, but requires that such services be negotiated in a separate agreement.

With these changes, the CeCILL is now fully enforceable according to WIPO rules, and according to French law in courts, without the legal problems remaining in GPL version 2 outside the United States.

The fact that it is protected by reputed public research centers (in France the INRIA, a founding member of the international W3 consortium, and the CEA working on atomic energy) which use them to publish their own open-source and free software, and by critical governmental organizations (which are also working in domains like military and defense systems) also gives much more security than using the GPL alone, as the license is supported officially by a government which is a full member of WIPO, and by an enforceable law.

Due to the huge cost of these French strategic systems, a very strong licensing scheme was absolutely necessary to help protecting these investments against illegitimate claims by other commercial third parties, and one of the first needs was to make the well-known open-source and free licenses fully compatible and protected under the French law and the many international treaties ratified by France.