Hi Angeline,
The main differences are:
1. The CE is free and open source, while the PE requires a subscription.
2. The PE contains additional features, and performance enhancements that not included in the CE.
3. The PE is supported, i.e. support is included in a PE subscription.
4. "Point releases" are made for the PE, which can include bug fixes, security fixes, and performance improvements, while only major releases are published for the CE.
You can find more about the differences, including details about the features included in the PE on:
http://www.orbeon.com/download. And for more on PE pricing, see:
http://www.orbeon.com/pricing.
I hope this helps,
Alex
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