The main paragraph of the OASIS-Open license says:
This document and translations of it may be copied and furnished to
others, and derivative works that comment on or otherwise explain it
or assist in its implementation may be prepared, copied, published,
and distributed, in whole or in part, without restriction of any
kind, provided that the above copyright notice and this section are
included on all such copies and derivative works. However, this
document itself may not be modified in any way, including by removing
the copyright notice or references to OASIS, except as needed for
the purpose of developing any document or deliverable produced by
an OASIS Technical Committee (in which case the rules applicable to
copyrights, as set forth in the OASIS IPR Policy, must be followed)
or as required to translate it into languages other than English.
The license is used for a couple of Relax-NG schemas included with app-emacs/org-mode (and with app-editors/emacs itself). Relax-NG provides an include mechanism allowing to override (i.e., add, modify or remove) any elements in the original file. The question is if this is equivalent to other free licenses that allow modifications to be shipped only as separate patches, with the original file being immutable.
Thread in the emacs-devel mailing list:
Currently I am also discussing this with Richard Stallman in a private conversation.