Yes, reverse-engineering is legal, except in some backwater countries

It has even been tested in court that a software license that prohibits reverse-engineering is not binding in Finland; you cannot be forced to honor such terms if embedded in the licencing agreement.

This comes pretty close to patents issue, I guess @reinob is the expert on the matter but in EU a patent in an innovation covers only the commercial exploitation of the patented feature.

This means that if one makes objects/software/services/whatever and sells them for a fee (I am not sure if it is necessary to make profit doing so?) then one needs to obtain a license from the patent holder; however if one makes and gives away for free, no license is required.