[locklock]

I don't think German Blue Cards are tied to a specific employer. As far as I know you only have to let the authority know if you change jobs less than a year after getting the card, and beyond that you just need to make above the money limit and you can work anywhere.

[gigatexal]

I had to when I changed jobs change it into the name of my new employer. But that was probably because I changed jobs before a year.