. The licence must allow modifications and derived works, and must allow them to be distributed under the same terms as the licence of the original software.
. The licence may restrict source code from being distributed in a modified form only if the licence allows the distribution of “patch files” with the source code for the purpose of modifying the program at build time.
. The licence must not discriminate against any person or group of persons.
. The licence must not restrict anyone from making use of the program in a specific field of endeavour.