We discussed that they will distribute my DarkSide lights in Europe and send them samples and we discussed few prototypes I had at that time. At some point they said that they're not interested and some time later to my disbelief they rolled out line of LED clearly made from my samples with on-PCB connector I showed them as engineering sample
I'm sorry, but WHAT THE F?? German Engineering my ...
As long as you have the proof, I would speak to a lawyer. If he is unwilling or unable to do anything, I would publish the evidence, but without making any accusations. Simply stating facts. Then send that to various tech sites in NA and Europe and hopefully they will cover the story.
I have to say, as someone that emigrated from Germany, I'm quite embarrassed by this.
I'm sure there's not many ways to make this sort of lighting, but if they got samples from you and then did this, that's quite shameful.