Hi, the Creative Commons (CY by 2.5) says:
You are free:
to Share — to copy, distribute and transmit the work
to Remix — to adapt the work
to make commercial use of the work
Under the following conditions:
Attribution — You must attribute the work in the manner specified by the author or licensor (but not in any way that suggests that they endorse you or your use of the work).
So yes - the links should remain intact in the manner specified by us.
But - for a small "donation fee" you are allowed to remove the copyright.
This can be found in Terms of use page.
For your consideration:
We had to introduce this fee some time ago since the donations are poor and by far not cover the costs of developing, server mantaining, support etc. So we hope you and also everyone else who will read this post understands this.
Thank you.