v41 has migrated to testing on 2015-05-06, why doesn't this get updated here ?

Your question is somewhat similar to
"Why is game-data-packager on Debian wheezy still on v30?"

Ubuntu is no rolling release.

When an Ubuntu release is published, it contains software in a certain version. And during the live cycle of that Ubuntu release there is no automatic upgrade to higher versions of the included software - unless:
it is software from a specific list (kernel, timezone data, firefox, thunderbird, java, and some more)
or there are important bug fixes or improvements that justify a SRU.

The options that you have for a higher version on vivid (or trusty or precise):

1. create a bug report stating that the new version has so much benefit or fixes severe bugs, that this justifies a SRU for vivid (unlikely that this will work) see https://wiki.ubuntu.com/StableReleaseUpdates for details of the process
2. Look in https://launchpad.net/ubuntu/+ppas?name_filter=game-data-packager to check whether someone else has already build a PPA with a higher version (I did not find any).
3. Create a PPA with game-data-packager v41 for vivid yourself
4. Download the original software and try compiling the software on your own system.
5. It might be possible to install the debian package on Ubuntu, but this can fail miserably and create all kinds of dependency problems.