It shouldn't, but for some agencies or state governments, it may.
And like most things with Asperger's, two sides of a coin. In some ways, being aspie would be a strength and help you be a better foster parent. In some other ways, it would be a liability that you'd need to make some good decisions in order to shore up.
And interest and dedication and motivation are among the most important factors. So, if you think you can do a good job as a foster parent, you probably can!
Note: NOT A PARENT, but an all-around good guy
Plus, a good friend of mine from high school was a foster kid.