There are a few reasons I released an open source version of CCE.

• To contribute to the open source community. My knowledge of development has been expanded by the open source community. I felt it was appropriate to give something back.
• I wanted to show the cryptocoin community how much the coin daemon RPC has improved over the years and what can be done with it.
• Of course on the business side, it is great PR. It can help draw attention to CCE and the upcoming 4.0 update.

In my view, the open source version is not particularly special in terms of coding and I think any moderately skilled programmer could have wrote it.
The open source version is very basic and truly meant as a foundation to build on. The full closed source version is more robust and much more feature rich.
CCE 3.99 already has many more features and a full API vs the open source version, including some of the commands needed for "lite" clients, the API will be further expanded in full version 4.0.

The open source version fits into CCE as I am planning on offering 4 tiers of explorers on CCE once the full version 4.0 is finished.
The free tier will basically be the open source version minus the two API commands and supported by ad revenue.
The removal of the API is mostly due to the fact the API calls do not generate ad revenue.
I may start setting up explorers on the free tier before the full version 4.0 is released on CCE.

More information on the full version 4.0 and cryptocoinexplorer.com will be in the official thread at:  https://bitcointalk.org/index.php?topic=922515.0.