The meaning of GPL

Like most of you I guess there is always the question of what am I allowed to do with GPL libraries.

I found an understandable blog about this topic which I summerize here it is based on MySQL, but basically, it is a description of GPL:

Here are some things the GPL allows:

• The GPL allows you to run a for-profit business on MySQL.
• The GPL allows you to modify the MySQL source code in any way you want.
• The GPL allows you to sell MySQL.
• The GPL allows you to redistribute MySQL.
• The GPL allows you to redistribute your modifications of MySQL.

Here are some things the GPL does not require:

• The GPL doesn’t require you to redistribute your modifications to MySQL.
• The GPL doesn’t require you to GPL-license any software that merely connects to MySQL.
• The GPL doesn’t require you to GPL-license all the software in your company.

So if you have to buy a commercial license for things the GPL doesn’t permit, what are those? Here are a couple of scenarios I can think of.

• You need a commercial license if you want to modify MySQL and redistribute the result as non-Free software.
• You need a commercial license if you want to embed MySQL within your non-Free program. Note that embed is not the same as “make a connection to.”