CapFriendly is relatively slick and user-friendly (for the hockey world), but it's funny to me how some in media are acting like it's this proprietary unicorn being snatched away forever.
An organization or entrepreneur could hire two engineers/developers for $150k each and recreate it within 6-12 months. All the data is public (and neatly organized until mid-July), someone just needs to create their own interface and tools. No reason there shouldn't be a functionally indistinguishable public replacement by this time next year, not to mention teams getting a wake up call and developing their own.
In the end, its just a database with players info/salaries.
If you had the all the player info in a spreadsheet or microsoft access DB, it's be relatively trivial to create a "working" model. The real issue is getting this information updated in real time/close to it. I'm sure the NHL has something that teams can reference that is official. The NHLPA site used to contract details on it (or salary at least), i'm not sure if it does now.
The UI/Front end is really just window dressing. Salaries put in a table and a sum function, with a bit more complexity baked in when looking at day to day cap spending. Getting the exact contract details (and getting it right), that is probably the challenge, but my guess is that isn't that hard to overcome.
I'm sure that since the announcement, hockey nerds world wide have been trying to get something to market quick. I'm not worried about it.