Question: > 
> **Possible Duplicate:**  
> 
> [Interface vs Base class](https://stackoverflow.com/questions/56867/interface-vs-base-class) 
> 
> 
> 

A class implementing an `interface` has to implement all the methods of the interface, `but` if that class is implementing an `abstract class` is it necessary to implement all `abstract methods`?  

**If not**, can we create the `object` of that class which is implementing the `Abstract class`???

Answer: 
Software released under GPL or LGPL might not be what you're looking for, just because it requires that your product will be released under the same license.

Here is an overview of licenses with tons of links to explanations: <http://en.wikipedia.org/wiki/Comparison_of_free_software_licenses>
Read the Wikipedia article on this. The section "Free and open source software" on this article explains your question.

[Wikipedia Article](http://en.wikipedia.org/wiki/Software_license)

You are going to get a critical decision. So it is much worth to spend some time on license types and getting a good understanding. It will make you more comfortable in selecting the components.

Check this [comparison](http://developer.kde.org/documentation/licensing/licenses_summary.html) as well.