That's actually 1.04, but GOG's internal numbering is off for Linux (although they use the same as Obsidian for Windows).
Just GOG being GOG.
If you already have 1.03 and don't like to dl the entire tarball again, you can also use the unofficial patch (see the gog forums), which is much smaller.
I still have the 1.2.0.3.
In that case I will probably wait for 1.05 and download the whole tarball again.