Like darkheart said,
I prefer the LGPL idea myself which means that the free bit you use (for example a dynamic lib and it's src) must stay open and free, as well as documentation of any modifications you do to the free bit. However, you can still have the freedom to protect & sell the parts that you have created if you choose to - as long as you abide rules set out in the LGPL.
This approach is MUCH better for people who write shareware / games etc and rely on a source of income from it.
GPL is a much stricter and infectious licence. Simply by linking to something that is GPL, means that its licence infects your product too. So, although you can sell it in some circumstances, you have to disclose the source for everything. People can still make large money from GPL in other ways, but to make it work financially you have to have either a very big presence or offer something else 'in combination' with it (Ie: you could release your game's app under the GPL, but sell the media)
I prefer the LGPL idea myself which means that the free bit you use (for example a dynamic lib and it's src) must stay open and free, as well as documentation of any modifications you do to the free bit. However, you can still have the freedom to protect & sell the parts that you have created if you choose to - as long as you abide rules set out in the LGPL.
This approach is MUCH better for people who write shareware / games etc and rely on a source of income from it.
GPL is a much stricter and infectious licence. Simply by linking to something that is GPL, means that its licence infects your product too. So, although you can sell it in some circumstances, you have to disclose the source for everything. People can still make large money from GPL in other ways, but to make it work financially you have to have either a very big presence or offer something else 'in combination' with it (Ie: you could release your game's app under the GPL, but sell the media)