@pernia The 3-clause BSD does restrict you from relicensing, as by default copyright law doesn't allow relicensing and the BSD-3 contains no clause that allows you to relicense.

You seem to be confusing proprietizing and relicensing.

The BSD-3 is less free than the GPLv3, as it places restrictions on running the software, which the GPLv3 doesn't require acceptance just to run the software.