The procedure below should not be necessary any more, if running a fresh install of the official Raspbian Jessie image. See also bobthechemist's comment.
This is what I did to install
wolfram-engine on my Raspberry Pi 2 running Raspbian 8 (jessie).
Download the latest available deb package and install it with
sudo dpkg -i wolfram-engine_10.0.2+2015020304_armhf.deb
This will install the package, but leave it unconfigured because of the missing
Open with a text editor the file
/var/lib/dpkg/status, find the
wolfram-engine section and look for the dependencies line, which should be
Depends: java7-runtime | java8-runtime, libatlas3-base (>= 3.8.4-9),
libpango1.0-0 (>= 1.30.0-1), libcairo2 (>= 1.12.2-3),
libglib2.0-0 (>= 2.33.12+really2.32.4-5), libffi5 (>= 3.0.10-3+b3),
libpixman-1-0 (>= 0.26.0-4+deb7u1), zlib1g (>= 1:1.2.7.dfsg-13),
libfontconfig1 (>= 2.9.0-7.1), libfreetype6 (>= 2.4.9-1.1), libpng12-0 (>= 1.2.49-1),
libexpat1 (>= 2.1.0-1+deb7u1), libuuid1 (>= 2.20.1-5.3),
libportaudio2, libharfbuzz0a (>= 0.9.19-1co2rpi2)
then delete the trailing
, libharfbuzz0a (>= 0.9.19-1co2rpi2).
Let the package configuration complete
sudo apt-get -f install
Logout and login so the desktop icons would appear.
Mathematica will work happily with the system library,
/usr/lib/arm-linux-gnueabihf/libharfbuzz.so.0 which is provided by the
libharfbuzz0b_0.9.35-2_armhf.deb package and should not break your system in any way.
The issue is mostly cosmetic, due to the name of the dependency being changed in an incompatible way in jessie. I expect it would be addressed in the next release.