Is there a proper moral way to treat wordpress related abandonware?

The ease with which you may create wordpress plugins and themes, combined with relatively long time of existence of wordpress, created a growing wave of abandonware (software which is not maintained by their legal owner, and sometimes it is not clear if they have one).

The bigger part of this abandonware are plugins and themes which were rarely used, and probably not many people are actually missing them, but one of my favorite themes “Almost Spring” have gone the way of the dodo and not only that it was not updated for a very long time, but now the blog of its creator has vanished as well.

I keep the source code of the theme and I would like to update it and release to the public, the question is how much should I follow the original licensing terms of the theme (even worse, there is no explicit license in the source files).  I prefer to release my code under a sort of BSD license, and I would like to remove the link to the creators site, as I don’t see any real reason to provide SEO for some unknown domain squatter.

The law is quite clear about it, and under the law I should preserve the original license. Yet I wonder, if there is no one to care enough to complain about me breaking the law, can I practically do whatever I wish with the code?