We need to carefully document the licence of figleaf in order to get Tahoe-LAFS into Ubuntu Karmic Koala. However, figleaf isn't really a part of Tahoe-LAFS per se -- this is just a "convenience copy" of a development tool. The quickest way to make Tahoe-LAFS acceptable for Karmic then, is to remove figleaf from the Tahoe-LAFS tarball itself. People who want to run figleaf on Tahoe-LAFS (as everyone should want) can install figleaf themselves. I haven't tested this -- there may be incompatibilities between upstream figleaf and the copy that we had here...
Note that using "whatever version of python the name 'python' maps to in the current shell environment" is more error-prone that specifying which python you mean, such as by executing "/usr/bin/python setup.py" instead of executing "./setup.py". When you build tahoe (by running "make") it will make a copy of bin/allmydata-tahoe in instdir/bin/allmydata-tahoe with the shebang line rewritten to execute the specific version of python that was used when building instead of to execute "/usr/bin/env python".
However, it seems better that the default for lazy people be "whatever 'python' means currently" instead of "whatever 'python' meant to the manufacturer of your operating system".