later to claim that my code shall be released under GPL because my eyes
    have touched GPL code.

Not that I expect to change what you do, but for the record, I just have
to say that such a concern is not sensible. What counts with copyright
is what is written, not what is in your brain. The law does not
recognize telepathy.

Also, such a concern has nothing to do with the GPL. You could have the
same fear about looking at anyone's code under any license other than
the one you prefer, whether that license is the LPPL, GPL, "Knuthian", etc.