Hans,
i am not quiet sure if they are opensource?
but the websites indicated these are free to use for personal use.I wanted to share them through their own source pages but i didn't cared for their web sites before so i didnt have the address because i downloaded these through GOOGLE.
Here are the source pages for these textures:
1.Bamboo texture.
source

2.Stone wall texture.
source
License agreement From the developer