Now that's a necro if you've ever seen one. The game got taken down in April 2018 by the dev, Edgebee Studios.
The reason for this necro, that will probably result in my wiener beeing cut off, is that I loved this game and spent hundreds of hours with it. I am not savvy enough to pull this off myself so I come to the source I think, can: is it somehow possible to play offline on your own? Here's a link to the swf. Not the direct download, just the wiki community portal, 3rd entry is the .swf.
https://cforge.fandom.com/wiki/Critter_Forge_Wiki_talk:Community_Portal

I am in contact with the devs right now to get the server sided info but honestly have no if idea if we get beyond the "nah, fu." stage. I'd pay a bit to get this pulled off just to have it as an offline game. Could someone tech savvy enlighten me if that's a lost case? Thanks in advance!

E: Thanks for the answers and PMs!

if the only thing that makes it unplayable is a sitelock, there are multiple tutorials for that here on konghack. but if it actually communicated with a server of some sort though, youd have to set things up so you are the server and handle all the requests and such. which is probably way more effort and time than any of us are willing to do, but if you really want to there are guides for reversing and then emulating a games servers around the internet, and a quick google search should bring them up. thats how most private servers get made.

I looked up the possibility to create a server for myself but lack the skills to obtain the required files & data / read it out from remaining data on other sites. That's where the dream died :>