[lelanthran]

> The GPL does put restriction on use.

No, it does not. It places restrictions on redistribution, not on use. You can use it no matter who or what you are.

> If you make modification to the code and do not share those modifications, you are constrained from using the code you modified.

Incorrect. You can modify and use it to your hearts content. You are only required to share your modifications source if you distribute the modified software.