How much does a pattern have to be altered?

[Tygermane]

So I have recently started crocheting my dolls to sell them.  All of them are made as I go.  I have lots of other amigurumi patterns that I would like to use to make dolls for selling too. Some of the creators are fine with selling the finished product, & some are totally against it.  I will be respecting those who do not want metro sell the finished product ( in case anybody was worried).  Now I have read that as long as the pattern is altered enough it's ok to sell the finished product.  So I guess what I'm asking is exactly how much does a pattern have to be altered in order for it to become useable? Or should I just stay away from this topic all together?
I know there are lots of different opinions on this, but please remember I am not looking out to steal or disrespect the artist of a pattern because I wouldn't want someone to do it to me.