Hello, mupdf 1.10 was released some days ago (2016-11-21), with changes that will probably impact the ebuild. Especially the possibility to disable javascript.
<http://mupdf.com/news>: MuPDF 1.10a (2016-11-28) Version 1.10a is a bug fix release. If you downloaded the windows release for 1.10 you should also upgrade, since the zip archive accidentally included the RC2 binaries instead of the final version. A bug with mutool and saving PDF files using the 'ascii' option has been fixed.
See https://github.com/gentoo/gentoo/pull/3108/
commit 290927105365ff1f2374f383d7135ecf17f41cb1 Author: Michael Weber <xmw@gentoo.org> Date: Mon Jan 23 01:31:02 2017 +0100 app-text/mupdf: Version bump (https://github.com/gentoo/gentoo/pull/3108, thanks charIes17). Package-Manager: Portage-2.3.3, Repoman-2.3.1