Finding good quality relevant links can be tough at times which is why some SEO providers utilize their clients websites to benefit theirs.
Let’s talk about the ethics behind this link:
This is an example of a web design company using a clients website to pass PageRank to theirs. There are two things wrong with this. First, using a clients website to benefit the provider is unethical and unnatural. Secondly it’s in violation of Google’s Webmaster Guidelines under link schemes:
Violation: Widely distributed links in the footers or templates of various sites
If asked, I am sure this particular web design firm would claim this is a link crediting their work however, if that was the case then they would do something like: Website Designed by: Company Name and even so, they would need to no-follow their link to make it an acceptable practice.