I don't think that's fraud, just being deceitful. I dont think this fraud either but after reading this blog post twice

http://blog.ziftr.com/goodbye-sign-to-mine-hello-proof-of-knowledge/

the more it sounds like spr was a test for this coin. If not a test coin then they certainly followed spr's progress. Their conclusions regarding "sign to mine" mirror exactly what happened with spread, whales only being to mine, trusted pools etc.  The timing of this post Feb 25 is pretty suspicious too. Isn't that around the time Mr spread disappeared?  Once their conclusion regarding sign to mine was reached there's no more need for spread. There's no mention of masternodes in ziftr (that I can find) but they would be stupid to not implement those.

But why wouldn't they just keep on developing spread, change it to proof of knowledge and change the name to match their company.

In the post they say they are going to release the code for sign to mine and if it matches spr, I guess we know what happened to Mr spread.  If they retract,  well I guess we know what happened to Mr spread. They could sufficiently change it and release it I guess but I bet there are some pretty good code detectives here. Looks like this is their github https://github.com/Ziftr

Read the blog post, maybe its just the conspiracy theorist in me but then again the timing and conclusions are just uncanny.